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	$131.68	13.466%	$149.412	$149.41	$149.40	$149.40
Purchase #2	$199.25	12.219%	$223.5964	$223.60	$223.60	$223.60
Purchase #3	$172.39	7.722%	$185.702	$185.70	$185.70	$185.70
Purchase #4	$137.99	4.546%	$144.263	$144.26	$144.25	$144.30
Purchase #5	$179.41	5.570%	$189.4031	$189.40	$189.40	$189.40
Purchase #6	$85.95	5.642%	$90.7993	$90.80	$90.80	$90.80
Purchase #7	$76.89	8.420%	$83.3641	$83.36	$83.35	$83.40
7 purchase totals =	$983.56		$1,066.5399	$1,066.53	$1,066.50	$1,066.60