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	$97.47	7.218%	$104.5054	$104.51	$104.50	$104.50
Purchase #2	$69.88	10.113%	$76.947	$76.95	$76.95	$76.90
Purchase #3	$171.95	4.562%	$179.7944	$179.79	$179.80	$179.80
Purchase #4	$170.27	13.815%	$193.7928	$193.79	$193.80	$193.80
Purchase #5	$137.57	10.403%	$151.8814	$151.88	$151.90	$151.90
Purchase #6	$72.61	12.793%	$81.899	$81.90	$81.90	$81.90
Purchase #7	$166.72	6.454%	$177.4801	$177.48	$177.50	$177.50
7 purchase totals =	$886.47		$966.3001	$966.30	$966.35	$966.30