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	$113.85	4.487%	$118.9584	$118.96	$118.95	$119.00
Purchase #2	$199.33	13.431%	$226.102	$226.10	$226.10	$226.10
Purchase #3	$223.25	10.749%	$247.2471	$247.25	$247.25	$247.20
Purchase #4	$173.67	8.658%	$188.7063	$188.71	$188.70	$188.70
Purchase #5	$86.90	4.363%	$90.6914	$90.69	$90.70	$90.70
Purchase #6	$106.72	4.313%	$111.3228	$111.32	$111.30	$111.30
Purchase #7	$33.39	6.547%	$35.576	$35.58	$35.60	$35.60
7 purchase totals =	$937.11		$1,018.6040	$1,018.61	$1,018.60	$1,018.60