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	$52.34	12.870%	$59.0762	$59.08	$59.10	$59.10
Purchase #2	$53.65	4.655%	$56.1474	$56.15	$56.15	$56.10
Purchase #3	$58.32	9.167%	$63.6662	$63.67	$63.65	$63.70
Purchase #4	$32.32	13.276%	$36.6108	$36.61	$36.60	$36.60
Purchase #5	$53.62	11.546%	$59.811	$59.81	$59.80	$59.80
Purchase #6	$42.31	7.485%	$45.4769	$45.48	$45.50	$45.50
Purchase #7	$222.87	8.631%	$242.1059	$242.11	$242.10	$242.10
7 purchase totals =	$515.43		$562.8944	$562.91	$562.90	$562.90