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	$128.33	9.771%	$140.8691	$140.87	$140.85	$140.90
Purchase #2	$34.54	7.568%	$37.154	$37.15	$37.15	$37.20
Purchase #3	$208.57	3.751%	$216.3935	$216.39	$216.40	$216.40
Purchase #4	$47.80	12.421%	$53.7372	$53.74	$53.75	$53.70
Purchase #5	$209.83	3.505%	$217.1845	$217.18	$217.20	$217.20
Purchase #6	$224.56	10.816%	$248.8484	$248.85	$248.85	$248.80
Purchase #7	$210.47	9.200%	$229.8332	$229.83	$229.85	$229.80
7 purchase totals =	$1,064.10		$1,144.0199	$1,144.01	$1,144.05	$1,144.00