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	$106.35	6.587%	$113.3553	$113.36	$113.35	$113.40
Purchase #2	$36.51	12.864%	$41.2066	$41.21	$41.20	$41.20
Purchase #3	$161.83	4.362%	$168.889	$168.89	$168.90	$168.90
Purchase #4	$31.34	7.344%	$33.6416	$33.64	$33.65	$33.60
Purchase #5	$230.44	10.788%	$255.2999	$255.30	$255.30	$255.30
Purchase #6	$159.87	9.375%	$174.8578	$174.86	$174.85	$174.90
Purchase #7	$243.51	9.184%	$265.874	$265.87	$265.85	$265.90
7 purchase totals =	$969.85		$1,053.1242	$1,053.13	$1,053.10	$1,053.20