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	$224.34	11.454%	$250.0359	$250.04	$250.05	$250.00
Purchase #2	$111.57	12.803%	$125.8543	$125.85	$125.85	$125.90
Purchase #3	$18.77	10.707%	$20.7797	$20.78	$20.80	$20.80
Purchase #4	$141.54	5.573%	$149.428	$149.43	$149.45	$149.40
Purchase #5	$140.25	5.641%	$148.1615	$148.16	$148.15	$148.20
Purchase #6	$63.79	4.170%	$66.45	$66.45	$66.45	$66.50
Purchase #7	$223.52	12.136%	$250.6464	$250.65	$250.65	$250.60
7 purchase totals =	$923.78		$1,011.3558	$1,011.36	$1,011.40	$1,011.40