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	$20.57	12.383%	$23.1172	$23.12	$23.10	$23.10
Purchase #2	$73.52	7.281%	$78.873	$78.87	$78.85	$78.90
Purchase #3	$227.67	12.757%	$256.7139	$256.71	$256.70	$256.70
Purchase #4	$6.66	11.179%	$7.4045	$7.40	$7.40	$7.40
Purchase #5	$69.40	3.590%	$71.8915	$71.89	$71.90	$71.90
Purchase #6	$66.30	5.246%	$69.7781	$69.78	$69.80	$69.80
Purchase #7	$13.73	13.121%	$15.5315	$15.53	$15.55	$15.50
7 purchase totals =	$477.85		$523.3097	$523.30	$523.30	$523.30