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	$120.78	3.256%	$124.7126	$124.71	$124.70	$124.70
Purchase #2	$73.72	4.577%	$77.0942	$77.09	$77.10	$77.10
Purchase #3	$188.91	11.103%	$209.8847	$209.88	$209.90	$209.90
Purchase #4	$108.97	5.217%	$114.655	$114.66	$114.65	$114.70
Purchase #5	$31.41	3.626%	$32.5489	$32.55	$32.55	$32.50
Purchase #6	$200.38	11.427%	$223.2774	$223.28	$223.30	$223.30
Purchase #7	$160.52	3.119%	$165.5266	$165.53	$165.55	$165.50
7 purchase totals =	$884.69		$947.6994	$947.70	$947.75	$947.70