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	$172.32	7.620%	$185.4508	$185.45	$185.45	$185.50
Purchase #2	$238.61	11.667%	$266.4486	$266.45	$266.45	$266.40
Purchase #3	$248.53	8.619%	$269.9508	$269.95	$269.95	$270.00
Purchase #4	$159.54	6.253%	$169.516	$169.52	$169.50	$169.50
Purchase #5	$218.78	13.752%	$248.8666	$248.87	$248.85	$248.90
Purchase #6	$83.44	11.618%	$93.1341	$93.13	$93.15	$93.10
Purchase #7	$18.84	7.851%	$20.3191	$20.32	$20.30	$20.30
7 purchase totals =	$1,140.06		$1,253.6860	$1,253.69	$1,253.65	$1,253.70