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	$216.51	5.616%	$228.6692	$228.67	$228.65	$228.70
Purchase #2	$126.49	3.519%	$130.9412	$130.94	$130.95	$130.90
Purchase #3	$79.63	13.696%	$90.5361	$90.54	$90.55	$90.50
Purchase #4	$62.71	7.678%	$67.5249	$67.52	$67.50	$67.50
Purchase #5	$32.51	10.411%	$35.8946	$35.89	$35.90	$35.90
Purchase #6	$111.39	13.798%	$126.7596	$126.76	$126.75	$126.80
Purchase #7	$117.48	10.204%	$129.4677	$129.47	$129.45	$129.50
7 purchase totals =	$746.72		$809.7933	$809.79	$809.75	$809.80