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	$38.97	11.105%	$43.2976	$43.30	$43.30	$43.30
Purchase #2	$77.43	13.827%	$88.1362	$88.14	$88.15	$88.10
Purchase #3	$245.96	11.530%	$274.3192	$274.32	$274.30	$274.30
Purchase #4	$217.46	4.633%	$227.5349	$227.53	$227.55	$227.50
Purchase #5	$93.45	8.217%	$101.1288	$101.13	$101.15	$101.10
Purchase #6	$236.73	7.826%	$255.2565	$255.26	$255.25	$255.30
Purchase #7	$17.98	7.463%	$19.3218	$19.32	$19.30	$19.30
7 purchase totals =	$927.98		$1,008.9950	$1,009.00	$1,009.00	$1,008.90