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	$91.81	3.323%	$94.8608	$94.86	$94.85	$94.90
Purchase #2	$172.73	4.324%	$180.1988	$180.20	$180.20	$180.20
Purchase #3	$152.69	11.641%	$170.4646	$170.46	$170.45	$170.50
Purchase #4	$88.39	13.520%	$100.3403	$100.34	$100.35	$100.30
Purchase #5	$21.81	11.821%	$24.3882	$24.39	$24.40	$24.40
Purchase #6	$101.42	4.285%	$105.7658	$105.77	$105.75	$105.80
Purchase #7	$135.85	12.131%	$152.33	$152.33	$152.35	$152.30
7 purchase totals =	$764.70		$828.3485	$828.35	$828.35	$828.40