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	$172.84	13.318%	$195.8588	$195.86	$195.85	$195.90
Purchase #2	$135.83	12.222%	$152.4311	$152.43	$152.45	$152.40
Purchase #3	$133.81	13.119%	$151.3645	$151.36	$151.35	$151.40
Purchase #4	$51.76	13.254%	$58.6203	$58.62	$58.60	$58.60
Purchase #5	$125.52	4.249%	$130.8533	$130.85	$130.85	$130.90
Purchase #6	$143.89	6.417%	$153.1234	$153.12	$153.10	$153.10
Purchase #7	$17.81	13.394%	$20.1955	$20.20	$20.20	$20.20
7 purchase totals =	$781.46		$862.4469	$862.44	$862.40	$862.50