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	$44.57	3.452%	$46.1086	$46.11	$46.10	$46.10
Purchase #2	$74.38	5.501%	$78.4716	$78.47	$78.45	$78.50
Purchase #3	$73.80	6.454%	$78.5631	$78.56	$78.55	$78.60
Purchase #4	$92.77	3.643%	$96.1496	$96.15	$96.15	$96.10
Purchase #5	$134.43	5.362%	$141.6381	$141.64	$141.65	$141.60
Purchase #6	$25.43	5.727%	$26.8864	$26.89	$26.90	$26.90
Purchase #7	$190.93	13.682%	$217.053	$217.05	$217.05	$217.10
7 purchase totals =	$636.31		$684.8704	$684.87	$684.85	$684.90