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	$248.88	10.636%	$275.3509	$275.35	$275.35	$275.40
Purchase #2	$82.37	7.628%	$88.6532	$88.65	$88.65	$88.70
Purchase #3	$29.77	9.284%	$32.5338	$32.53	$32.55	$32.50
Purchase #4	$84.96	12.659%	$95.7151	$95.72	$95.70	$95.70
Purchase #5	$55.45	3.374%	$57.3209	$57.32	$57.30	$57.30
Purchase #6	$162.71	3.475%	$168.3642	$168.36	$168.35	$168.40
Purchase #7	$143.76	5.155%	$151.1708	$151.17	$151.15	$151.20
7 purchase totals =	$807.90		$869.1089	$869.10	$869.05	$869.20