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	$208.51	8.148%	$225.4994	$225.50	$225.50	$225.50
Purchase #2	$234.45	13.367%	$265.7889	$265.79	$265.80	$265.80
Purchase #3	$177.44	7.683%	$191.0727	$191.07	$191.05	$191.10
Purchase #4	$46.33	12.477%	$52.1106	$52.11	$52.10	$52.10
Purchase #5	$22.27	13.769%	$25.3364	$25.34	$25.35	$25.30
Purchase #6	$188.27	11.816%	$210.516	$210.52	$210.50	$210.50
Purchase #7	$74.29	10.819%	$82.3274	$82.33	$82.35	$82.30
7 purchase totals =	$951.56		$1,052.6514	$1,052.66	$1,052.65	$1,052.60