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	$241.61	13.779%	$274.9014	$274.90	$274.90	$274.90
Purchase #2	$50.78	9.157%	$55.4299	$55.43	$55.45	$55.40
Purchase #3	$13.87	11.223%	$15.4266	$15.43	$15.45	$15.40
Purchase #4	$236.50	13.775%	$269.0779	$269.08	$269.10	$269.10
Purchase #5	$146.71	8.583%	$159.3021	$159.30	$159.30	$159.30
Purchase #6	$61.82	13.369%	$70.0847	$70.08	$70.10	$70.10
Purchase #7	$221.53	9.782%	$243.2001	$243.20	$243.20	$243.20
7 purchase totals =	$972.82		$1,087.4227	$1,087.42	$1,087.50	$1,087.40