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	$7.25	8.331%	$7.854	$7.85	$7.85	$7.90
Purchase #2	$87.33	13.712%	$99.3047	$99.30	$99.30	$99.30
Purchase #3	$235.31	10.300%	$259.5469	$259.55	$259.55	$259.50
Purchase #4	$238.71	13.555%	$271.0671	$271.07	$271.05	$271.10
Purchase #5	$155.90	3.526%	$161.397	$161.40	$161.40	$161.40
Purchase #6	$87.43	11.278%	$97.2904	$97.29	$97.30	$97.30
Purchase #7	$131.60	13.210%	$148.9844	$148.98	$149.00	$149.00
7 purchase totals =	$943.53		$1,045.4445	$1,045.44	$1,045.45	$1,045.50