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	$172.53	7.253%	$185.0436	$185.04	$185.05	$185.00
Purchase #2	$185.67	3.174%	$191.5632	$191.56	$191.55	$191.60
Purchase #3	$11.73	10.482%	$12.9595	$12.96	$12.95	$13.00
Purchase #4	$70.79	9.428%	$77.4641	$77.46	$77.45	$77.50
Purchase #5	$32.73	10.819%	$36.2711	$36.27	$36.25	$36.30
Purchase #6	$213.50	10.776%	$236.5068	$236.51	$236.50	$236.50
Purchase #7	$108.50	3.640%	$112.4494	$112.45	$112.45	$112.40
7 purchase totals =	$795.45		$852.2577	$852.25	$852.20	$852.30