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	$200.62	10.363%	$221.4103	$221.41	$221.40	$221.40
Purchase #2	$212.38	9.837%	$233.2718	$233.27	$233.25	$233.30
Purchase #3	$221.89	10.598%	$245.4059	$245.41	$245.40	$245.40
Purchase #4	$164.51	9.369%	$179.9229	$179.92	$179.90	$179.90
Purchase #5	$163.53	10.597%	$180.8593	$180.86	$180.85	$180.90
Purchase #6	$204.34	13.197%	$231.3067	$231.31	$231.30	$231.30
Purchase #7	$197.66	12.462%	$222.2924	$222.29	$222.30	$222.30
7 purchase totals =	$1,364.93		$1,514.4693	$1,514.47	$1,514.40	$1,514.50