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	$188.90	6.177%	$200.5684	$200.57	$200.55	$200.60
Purchase #2	$36.53	13.462%	$41.4477	$41.45	$41.45	$41.40
Purchase #3	$148.56	11.398%	$165.4929	$165.49	$165.50	$165.50
Purchase #4	$138.34	4.331%	$144.3315	$144.33	$144.35	$144.30
Purchase #5	$33.64	11.585%	$37.5372	$37.54	$37.55	$37.50
Purchase #6	$242.51	5.713%	$256.3646	$256.36	$256.35	$256.40
Purchase #7	$179.66	9.401%	$196.5498	$196.55	$196.55	$196.50
7 purchase totals =	$968.14		$1,042.2921	$1,042.29	$1,042.30	$1,042.20