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	$116.29	13.432%	$131.9101	$131.91	$131.90	$131.90
Purchase #2	$53.45	8.575%	$58.0333	$58.03	$58.05	$58.00
Purchase #3	$172.69	10.413%	$190.6722	$190.67	$190.65	$190.70
Purchase #4	$148.73	12.469%	$167.2751	$167.28	$167.30	$167.30
Purchase #5	$110.67	13.363%	$125.4588	$125.46	$125.45	$125.50
Purchase #6	$157.65	11.573%	$175.8948	$175.89	$175.90	$175.90
Purchase #7	$161.90	5.189%	$170.301	$170.30	$170.30	$170.30
7 purchase totals =	$921.38		$1,019.5453	$1,019.54	$1,019.55	$1,019.60