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	$193.95	5.363%	$204.3515	$204.35	$204.35	$204.40
Purchase #2	$37.72	11.456%	$42.0412	$42.04	$42.05	$42.00
Purchase #3	$115.30	13.373%	$130.7191	$130.72	$130.70	$130.70
Purchase #4	$107.55	4.453%	$112.3392	$112.34	$112.35	$112.30
Purchase #5	$222.41	12.747%	$250.7606	$250.76	$250.75	$250.80
Purchase #6	$131.94	7.865%	$142.3171	$142.32	$142.30	$142.30
Purchase #7	$239.66	10.130%	$263.9376	$263.94	$263.95	$263.90
7 purchase totals =	$1,048.53		$1,146.4663	$1,146.47	$1,146.45	$1,146.40