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	$203.30	12.489%	$228.6901	$228.69	$228.70	$228.70
Purchase #2	$81.44	9.864%	$89.4732	$89.47	$89.45	$89.50
Purchase #3	$56.43	9.408%	$61.7389	$61.74	$61.75	$61.70
Purchase #4	$52.77	5.486%	$55.665	$55.67	$55.65	$55.70
Purchase #5	$217.39	6.584%	$231.703	$231.70	$231.70	$231.70
Purchase #6	$123.38	6.626%	$131.5552	$131.56	$131.55	$131.60
Purchase #7	$96.51	3.106%	$99.5076	$99.51	$99.50	$99.50
7 purchase totals =	$831.22		$898.3330	$898.34	$898.30	$898.40