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	$100.96	4.294%	$105.2952	$105.30	$105.30	$105.30
Purchase #2	$205.71	11.448%	$229.2597	$229.26	$229.25	$229.30
Purchase #3	$158.65	12.214%	$178.0275	$178.03	$178.05	$178.00
Purchase #4	$48.38	13.697%	$55.0066	$55.01	$55.00	$55.00
Purchase #5	$170.72	8.674%	$185.5283	$185.53	$185.55	$185.50
Purchase #6	$124.39	5.181%	$130.8346	$130.83	$130.85	$130.80
Purchase #7	$213.50	4.110%	$222.2749	$222.27	$222.25	$222.30
7 purchase totals =	$1,022.31		$1,106.2268	$1,106.23	$1,106.25	$1,106.20