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	$79.51	7.666%	$85.6052	$85.61	$85.60	$85.60
Purchase #2	$139.27	13.514%	$158.0909	$158.09	$158.10	$158.10
Purchase #3	$186.33	9.700%	$204.404	$204.40	$204.40	$204.40
Purchase #4	$22.79	13.428%	$25.8502	$25.85	$25.85	$25.90
Purchase #5	$103.38	9.807%	$113.5185	$113.52	$113.50	$113.50
Purchase #6	$120.37	11.810%	$134.5857	$134.59	$134.60	$134.60
Purchase #7	$204.98	9.389%	$224.2256	$224.23	$224.25	$224.20
7 purchase totals =	$856.63		$946.2801	$946.29	$946.30	$946.30