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	$213.43	4.151%	$222.2895	$222.29	$222.30	$222.30
Purchase #2	$219.32	11.361%	$244.2369	$244.24	$244.25	$244.20
Purchase #3	$188.33	4.324%	$196.4734	$196.47	$196.45	$196.50
Purchase #4	$133.78	13.203%	$151.443	$151.44	$151.45	$151.40
Purchase #5	$54.50	7.255%	$58.454	$58.45	$58.45	$58.50
Purchase #6	$10.84	4.440%	$11.3213	$11.32	$11.30	$11.30
Purchase #7	$75.53	9.527%	$82.7257	$82.73	$82.75	$82.70
7 purchase totals =	$895.73		$966.9438	$966.94	$966.95	$966.90