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	$188.32	7.410%	$202.2745	$202.27	$202.25	$202.30
Purchase #2	$18.93	3.699%	$19.6302	$19.63	$19.65	$19.60
Purchase #3	$74.97	11.358%	$83.4851	$83.49	$83.50	$83.50
Purchase #4	$203.40	3.527%	$210.5739	$210.57	$210.55	$210.60
Purchase #5	$133.95	13.109%	$151.5095	$151.51	$151.50	$151.50
Purchase #6	$148.72	13.575%	$168.9087	$168.91	$168.90	$168.90
Purchase #7	$132.89	13.577%	$150.9325	$150.93	$150.95	$150.90
7 purchase totals =	$901.18		$987.3144	$987.31	$987.30	$987.30