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	$175.33	12.284%	$196.8675	$196.87	$196.85	$196.90
Purchase #2	$219.32	12.624%	$247.007	$247.01	$247.00	$247.00
Purchase #3	$111.86	4.300%	$116.67	$116.67	$116.65	$116.70
Purchase #4	$6.39	3.635%	$6.6223	$6.62	$6.60	$6.60
Purchase #5	$41.32	6.114%	$43.8463	$43.85	$43.85	$43.80
Purchase #6	$224.74	10.379%	$248.0658	$248.07	$248.05	$248.10
Purchase #7	$48.90	7.702%	$52.6663	$52.67	$52.65	$52.70
7 purchase totals =	$827.86		$911.7452	$911.76	$911.65	$911.80