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	$197.59	10.280%	$217.9023	$217.90	$217.90	$217.90
Purchase #2	$224.78	11.268%	$250.1082	$250.11	$250.10	$250.10
Purchase #3	$47.42	11.256%	$52.7576	$52.76	$52.75	$52.80
Purchase #4	$40.55	7.215%	$43.4757	$43.48	$43.50	$43.50
Purchase #5	$105.44	5.338%	$111.0684	$111.07	$111.05	$111.10
Purchase #6	$87.91	7.762%	$94.7336	$94.73	$94.75	$94.70
Purchase #7	$174.86	9.515%	$191.4979	$191.50	$191.50	$191.50
7 purchase totals =	$878.55		$961.5437	$961.55	$961.55	$961.60