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	$225.57	11.583%	$251.6978	$251.70	$251.70	$251.70
Purchase #2	$166.40	13.348%	$188.6111	$188.61	$188.60	$188.60
Purchase #3	$82.46	11.478%	$91.9248	$91.92	$91.90	$91.90
Purchase #4	$90.45	13.390%	$102.5613	$102.56	$102.55	$102.60
Purchase #5	$93.47	6.282%	$99.3418	$99.34	$99.35	$99.30
Purchase #6	$130.62	11.786%	$146.0149	$146.01	$146.00	$146.00
Purchase #7	$140.53	10.855%	$155.7845	$155.78	$155.80	$155.80
7 purchase totals =	$929.50		$1,035.9362	$1,035.92	$1,035.90	$1,035.90