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	$116.89	12.826%	$131.8823	$131.88	$131.90	$131.90
Purchase #2	$239.67	12.543%	$269.7318	$269.73	$269.75	$269.70
Purchase #3	$41.69	7.217%	$44.6988	$44.70	$44.70	$44.70
Purchase #4	$171.69	5.336%	$180.8514	$180.85	$180.85	$180.90
Purchase #5	$176.77	8.318%	$191.4737	$191.47	$191.45	$191.50
Purchase #6	$134.46	8.636%	$146.072	$146.07	$146.05	$146.10
Purchase #7	$58.33	4.570%	$60.9957	$61.00	$61.00	$61.00
7 purchase totals =	$939.50		$1,025.7057	$1,025.70	$1,025.70	$1,025.80