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	$206.31	7.423%	$221.6244	$221.62	$221.60	$221.60
Purchase #2	$72.33	6.611%	$77.1117	$77.11	$77.10	$77.10
Purchase #3	$137.39	11.212%	$152.7942	$152.79	$152.80	$152.80
Purchase #4	$125.29	7.532%	$134.7268	$134.73	$134.75	$134.70
Purchase #5	$169.67	9.134%	$185.1677	$185.17	$185.15	$185.20
Purchase #6	$93.65	10.702%	$103.6724	$103.67	$103.65	$103.70
Purchase #7	$145.30	3.325%	$150.1312	$150.13	$150.15	$150.10
7 purchase totals =	$949.94		$1,025.2284	$1,025.22	$1,025.20	$1,025.20