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	$64.46	10.311%	$71.1065	$71.11	$71.10	$71.10
Purchase #2	$214.54	3.630%	$222.3278	$222.33	$222.35	$222.30
Purchase #3	$153.90	3.867%	$159.8513	$159.85	$159.85	$159.90
Purchase #4	$234.90	10.311%	$259.1205	$259.12	$259.10	$259.10
Purchase #5	$225.66	13.480%	$256.079	$256.08	$256.10	$256.10
Purchase #6	$144.73	4.166%	$150.7595	$150.76	$150.75	$150.80
Purchase #7	$241.31	11.141%	$268.1943	$268.19	$268.20	$268.20
7 purchase totals =	$1,279.50		$1,387.4389	$1,387.44	$1,387.45	$1,387.50