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	$135.61	12.490%	$152.5477	$152.55	$152.55	$152.50
Purchase #2	$136.34	7.409%	$146.4414	$146.44	$146.45	$146.40
Purchase #3	$32.61	13.229%	$36.924	$36.92	$36.90	$36.90
Purchase #4	$120.49	7.249%	$129.2243	$129.22	$129.20	$129.20
Purchase #5	$233.91	12.287%	$262.6505	$262.65	$262.65	$262.70
Purchase #6	$75.95	9.199%	$82.9366	$82.94	$82.95	$82.90
Purchase #7	$176.80	11.308%	$196.7925	$196.79	$196.80	$196.80
7 purchase totals =	$911.71		$1,007.5170	$1,007.51	$1,007.50	$1,007.40