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	$173.91	10.760%	$192.6227	$192.62	$192.60	$192.60
Purchase #2	$40.84	10.874%	$45.2809	$45.28	$45.30	$45.30
Purchase #3	$170.81	6.695%	$182.2457	$182.25	$182.25	$182.20
Purchase #4	$132.46	3.388%	$136.9477	$136.95	$136.95	$136.90
Purchase #5	$78.88	9.638%	$86.4825	$86.48	$86.50	$86.50
Purchase #6	$231.87	9.801%	$254.5956	$254.60	$254.60	$254.60
Purchase #7	$228.77	10.842%	$253.5732	$253.57	$253.55	$253.60
7 purchase totals =	$1,057.54		$1,151.7483	$1,151.75	$1,151.75	$1,151.70