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	$122.75	3.518%	$127.0683	$127.07	$127.05	$127.10
Purchase #2	$148.84	10.772%	$164.873	$164.87	$164.85	$164.90
Purchase #3	$24.72	12.793%	$27.8824	$27.88	$27.90	$27.90
Purchase #4	$199.36	10.433%	$220.1592	$220.16	$220.15	$220.20
Purchase #5	$151.56	13.325%	$171.7554	$171.76	$171.75	$171.80
Purchase #6	$137.91	8.182%	$149.1938	$149.19	$149.20	$149.20
Purchase #7	$37.82	13.707%	$43.004	$43.00	$43.00	$43.00
7 purchase totals =	$822.96		$903.9361	$903.93	$903.90	$904.10