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	$70.48	10.563%	$77.9248	$77.92	$77.90	$77.90
Purchase #2	$155.70	8.138%	$168.3709	$168.37	$168.35	$168.40
Purchase #3	$135.67	11.834%	$151.7252	$151.73	$151.75	$151.70
Purchase #4	$153.73	13.429%	$174.3744	$174.37	$174.35	$174.40
Purchase #5	$136.69	11.463%	$152.3588	$152.36	$152.35	$152.40
Purchase #6	$169.46	4.721%	$177.4602	$177.46	$177.45	$177.50
Purchase #7	$173.53	9.847%	$190.6175	$190.62	$190.60	$190.60
7 purchase totals =	$995.26		$1,092.8318	$1,092.83	$1,092.75	$1,092.90