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	$245.60	11.625%	$274.151	$274.15	$274.15	$274.20
Purchase #2	$57.44	7.184%	$61.5665	$61.57	$61.55	$61.60
Purchase #3	$237.52	6.857%	$253.8067	$253.81	$253.80	$253.80
Purchase #4	$28.59	13.322%	$32.3988	$32.40	$32.40	$32.40
Purchase #5	$144.66	10.630%	$160.0374	$160.04	$160.05	$160.00
Purchase #6	$46.30	10.521%	$51.1712	$51.17	$51.15	$51.20
Purchase #7	$128.30	8.644%	$139.3903	$139.39	$139.40	$139.40
7 purchase totals =	$888.41		$972.5219	$972.53	$972.50	$972.60