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	$81.83	13.593%	$92.9532	$92.95	$92.95	$93.00
Purchase #2	$175.47	9.358%	$191.8905	$191.89	$191.90	$191.90
Purchase #3	$133.78	7.317%	$143.5687	$143.57	$143.55	$143.60
Purchase #4	$16.65	9.399%	$18.2149	$18.21	$18.20	$18.20
Purchase #5	$40.84	4.778%	$42.7913	$42.79	$42.80	$42.80
Purchase #6	$168.52	13.594%	$191.4286	$191.43	$191.45	$191.40
Purchase #7	$98.49	13.118%	$111.4099	$111.41	$111.40	$111.40
7 purchase totals =	$715.58		$792.2571	$792.25	$792.25	$792.30