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	$235.42	13.479%	$267.1523	$267.15	$267.15	$267.20
Purchase #2	$9.31	10.806%	$10.316	$10.32	$10.30	$10.30
Purchase #3	$78.58	8.266%	$85.0754	$85.08	$85.10	$85.10
Purchase #4	$216.83	8.818%	$235.9501	$235.95	$235.95	$236.00
Purchase #5	$203.65	5.714%	$215.2866	$215.29	$215.30	$215.30
Purchase #6	$65.60	10.176%	$72.2755	$72.28	$72.30	$72.30
Purchase #7	$145.66	10.368%	$160.762	$160.76	$160.75	$160.80
7 purchase totals =	$955.05		$1,046.8179	$1,046.83	$1,046.85	$1,047.00