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	$186.69	6.235%	$198.3301	$198.33	$198.35	$198.30
Purchase #2	$193.91	7.769%	$208.9749	$208.97	$208.95	$209.00
Purchase #3	$130.36	11.626%	$145.5157	$145.52	$145.50	$145.50
Purchase #4	$236.84	13.709%	$269.3084	$269.31	$269.30	$269.30
Purchase #5	$83.30	8.555%	$90.4263	$90.43	$90.45	$90.40
Purchase #6	$114.34	11.555%	$127.552	$127.55	$127.55	$127.60
Purchase #7	$188.72	13.152%	$213.5405	$213.54	$213.55	$213.50
7 purchase totals =	$1,134.16		$1,253.6479	$1,253.65	$1,253.65	$1,253.60