Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$120.55	9.361%	$131.8347	$131.83	$131.85	$131.80
Purchase #2	$179.45	9.629%	$196.7292	$196.73	$196.75	$196.70
Purchase #3	$217.70	5.273%	$229.1793	$229.18	$229.20	$229.20
Purchase #4	$105.31	13.392%	$119.4131	$119.41	$119.40	$119.40
Purchase #5	$131.56	9.403%	$143.9306	$143.93	$143.95	$143.90
Purchase #6	$156.33	10.543%	$172.8119	$172.81	$172.80	$172.80
Purchase #7	$153.85	12.857%	$173.6305	$173.63	$173.65	$173.60
7 purchase totals =	$1,064.75		$1,167.5293	$1,167.52	$1,167.60	$1,167.40