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	$245.58	5.407%	$258.8585	$258.86	$258.85	$258.90
Purchase #2	$209.98	10.632%	$232.3051	$232.31	$232.30	$232.30
Purchase #3	$243.68	11.227%	$271.038	$271.04	$271.05	$271.00
Purchase #4	$19.31	11.458%	$21.5225	$21.52	$21.50	$21.50
Purchase #5	$168.25	13.745%	$191.376	$191.38	$191.40	$191.40
Purchase #6	$33.26	12.660%	$37.4707	$37.47	$37.45	$37.50
Purchase #7	$211.41	12.492%	$237.8193	$237.82	$237.80	$237.80
7 purchase totals =	$1,131.47		$1,250.3901	$1,250.40	$1,250.35	$1,250.40