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	$28.96	10.579%	$32.0237	$32.02	$32.00	$32.00
Purchase #2	$32.44	3.618%	$33.6137	$33.61	$33.60	$33.60
Purchase #3	$41.72	11.431%	$46.489	$46.49	$46.50	$46.50
Purchase #4	$144.80	11.331%	$161.2073	$161.21	$161.20	$161.20
Purchase #5	$132.83	10.375%	$146.6111	$146.61	$146.60	$146.60
Purchase #6	$206.90	12.839%	$233.4639	$233.46	$233.45	$233.50
Purchase #7	$85.80	9.355%	$93.8266	$93.83	$93.85	$93.80
7 purchase totals =	$673.45		$747.2353	$747.23	$747.20	$747.20