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	$234.26	4.817%	$245.5443	$245.54	$245.55	$245.50
Purchase #2	$182.94	8.552%	$198.585	$198.59	$198.60	$198.60
Purchase #3	$47.30	12.558%	$53.2399	$53.24	$53.25	$53.20
Purchase #4	$236.53	13.139%	$267.6077	$267.61	$267.60	$267.60
Purchase #5	$93.62	12.353%	$105.1849	$105.18	$105.20	$105.20
Purchase #6	$93.29	5.501%	$98.4219	$98.42	$98.40	$98.40
Purchase #7	$60.52	10.530%	$66.8928	$66.89	$66.90	$66.90
7 purchase totals =	$948.46		$1,035.4765	$1,035.47	$1,035.50	$1,035.40