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	$90.34	6.146%	$95.8923	$95.89	$95.90	$95.90
Purchase #2	$37.84	4.565%	$39.5674	$39.57	$39.55	$39.60
Purchase #3	$199.82	9.406%	$218.6151	$218.62	$218.60	$218.60
Purchase #4	$176.26	4.735%	$184.6059	$184.61	$184.60	$184.60
Purchase #5	$33.35	9.675%	$36.5766	$36.58	$36.60	$36.60
Purchase #6	$239.27	9.738%	$262.5701	$262.57	$262.55	$262.60
Purchase #7	$242.63	8.629%	$263.5665	$263.57	$263.55	$263.60
7 purchase totals =	$1,019.51		$1,101.3939	$1,101.41	$1,101.35	$1,101.50