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	$172.45	9.103%	$188.1481	$188.15	$188.15	$188.10
Purchase #2	$127.27	3.695%	$131.9726	$131.97	$131.95	$132.00
Purchase #3	$160.34	3.258%	$165.5639	$165.56	$165.55	$165.60
Purchase #4	$191.76	7.843%	$206.7997	$206.80	$206.80	$206.80
Purchase #5	$173.35	6.851%	$185.2262	$185.23	$185.25	$185.20
Purchase #6	$122.47	6.556%	$130.4991	$130.50	$130.50	$130.50
Purchase #7	$114.66	4.130%	$119.3955	$119.40	$119.40	$119.40
7 purchase totals =	$1,062.30		$1,127.6051	$1,127.61	$1,127.60	$1,127.60