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	$134.47	12.520%	$151.3056	$151.31	$151.30	$151.30
Purchase #2	$123.91	11.309%	$137.923	$137.92	$137.90	$137.90
Purchase #3	$212.96	11.368%	$237.1693	$237.17	$237.15	$237.20
Purchase #4	$108.31	10.359%	$119.5298	$119.53	$119.55	$119.50
Purchase #5	$78.63	5.197%	$82.7164	$82.72	$82.70	$82.70
Purchase #6	$220.27	13.662%	$250.3633	$250.36	$250.35	$250.40
Purchase #7	$59.63	13.404%	$67.6228	$67.62	$67.60	$67.60
7 purchase totals =	$938.18		$1,046.6302	$1,046.63	$1,046.55	$1,046.60