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	$127.83	11.487%	$142.5138	$142.51	$142.50	$142.50
Purchase #2	$64.97	12.389%	$73.0191	$73.02	$73.00	$73.00
Purchase #3	$226.71	11.831%	$253.5321	$253.53	$253.55	$253.50
Purchase #4	$24.34	10.477%	$26.8901	$26.89	$26.90	$26.90
Purchase #5	$127.75	10.589%	$141.2774	$141.28	$141.30	$141.30
Purchase #6	$146.42	3.567%	$151.6428	$151.64	$151.65	$151.60
Purchase #7	$76.61	11.186%	$85.1796	$85.18	$85.20	$85.20
7 purchase totals =	$794.63		$874.0549	$874.05	$874.10	$874.00