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	$222.27	10.367%	$245.3127	$245.31	$245.30	$245.30
Purchase #2	$227.61	9.630%	$249.5288	$249.53	$249.55	$249.50
Purchase #3	$229.70	7.731%	$247.4581	$247.46	$247.45	$247.50
Purchase #4	$220.30	13.810%	$250.7234	$250.72	$250.70	$250.70
Purchase #5	$93.69	7.165%	$100.4029	$100.40	$100.40	$100.40
Purchase #6	$174.26	9.134%	$190.1769	$190.18	$190.20	$190.20
Purchase #7	$195.74	7.735%	$210.8805	$210.88	$210.90	$210.90
7 purchase totals =	$1,363.57		$1,494.4833	$1,494.48	$1,494.50	$1,494.50