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	$75.37	13.419%	$85.4839	$85.48	$85.50	$85.50
Purchase #2	$5.29	6.127%	$5.6141	$5.61	$5.60	$5.60
Purchase #3	$39.47	11.104%	$43.8527	$43.85	$43.85	$43.90
Purchase #4	$72.60	10.317%	$80.0901	$80.09	$80.10	$80.10
Purchase #5	$126.33	3.784%	$131.1103	$131.11	$131.10	$131.10
Purchase #6	$228.63	8.303%	$247.6131	$247.61	$247.60	$247.60
Purchase #7	$143.92	8.365%	$155.9589	$155.96	$155.95	$156.00
7 purchase totals =	$691.61		$749.7231	$749.71	$749.70	$749.80