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	$97.95	13.681%	$111.3505	$111.35	$111.35	$111.40
Purchase #2	$155.88	8.159%	$168.5982	$168.60	$168.60	$168.60
Purchase #3	$70.84	10.113%	$78.004	$78.00	$78.00	$78.00
Purchase #4	$240.95	8.505%	$261.4428	$261.44	$261.45	$261.40
Purchase #5	$145.56	9.371%	$159.2004	$159.20	$159.20	$159.20
Purchase #6	$213.79	6.434%	$227.5452	$227.55	$227.55	$227.50
Purchase #7	$159.66	6.341%	$169.784	$169.78	$169.80	$169.80
7 purchase totals =	$1,084.63		$1,175.9251	$1,175.92	$1,175.95	$1,175.90