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	$143.59	5.486%	$151.4673	$151.47	$151.45	$151.50
Purchase #2	$175.52	13.345%	$198.9431	$198.94	$198.95	$198.90
Purchase #3	$124.46	5.587%	$131.4136	$131.41	$131.40	$131.40
Purchase #4	$203.84	3.191%	$210.3445	$210.34	$210.35	$210.30
Purchase #5	$209.40	6.548%	$223.1115	$223.11	$223.10	$223.10
Purchase #6	$222.96	3.739%	$231.2965	$231.30	$231.30	$231.30
Purchase #7	$114.49	12.533%	$128.839	$128.84	$128.85	$128.80
7 purchase totals =	$1,194.26		$1,275.4155	$1,275.41	$1,275.40	$1,275.30