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	$35.26	5.271%	$37.1186	$37.12	$37.10	$37.10
Purchase #2	$141.62	13.410%	$160.6112	$160.61	$160.60	$160.60
Purchase #3	$195.62	6.550%	$208.4331	$208.43	$208.45	$208.40
Purchase #4	$248.59	13.590%	$282.3734	$282.37	$282.35	$282.40
Purchase #5	$142.60	11.309%	$158.7266	$158.73	$158.75	$158.70
Purchase #6	$35.83	7.597%	$38.552	$38.55	$38.55	$38.60
Purchase #7	$134.94	10.379%	$148.9454	$148.95	$148.95	$148.90
7 purchase totals =	$934.46		$1,034.7603	$1,034.76	$1,034.75	$1,034.70