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	$101.96	9.484%	$111.6299	$111.63	$111.65	$111.60
Purchase #2	$152.66	11.567%	$170.3182	$170.32	$170.30	$170.30
Purchase #3	$249.67	10.476%	$275.8254	$275.83	$275.85	$275.80
Purchase #4	$84.62	7.757%	$91.184	$91.18	$91.20	$91.20
Purchase #5	$154.31	8.373%	$167.2304	$167.23	$167.25	$167.20
Purchase #6	$84.38	9.827%	$92.672	$92.67	$92.65	$92.70
Purchase #7	$131.50	4.320%	$137.1808	$137.18	$137.20	$137.20
7 purchase totals =	$959.10		$1,046.0407	$1,046.04	$1,046.10	$1,046.00