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	$32.89	12.606%	$37.0361	$37.04	$37.05	$37.00
Purchase #2	$186.55	10.365%	$205.8859	$205.89	$205.90	$205.90
Purchase #3	$221.78	11.220%	$246.6637	$246.66	$246.65	$246.70
Purchase #4	$164.66	12.583%	$185.3792	$185.38	$185.40	$185.40
Purchase #5	$66.77	6.560%	$71.1501	$71.15	$71.15	$71.20
Purchase #6	$189.73	6.723%	$202.4855	$202.49	$202.50	$202.50
Purchase #7	$164.27	13.152%	$185.8748	$185.87	$185.85	$185.90
7 purchase totals =	$1,026.65		$1,134.4753	$1,134.48	$1,134.50	$1,134.60