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	$73.62	6.152%	$78.1491	$78.15	$78.15	$78.10
Purchase #2	$169.68	8.275%	$183.721	$183.72	$183.70	$183.70
Purchase #3	$145.54	3.802%	$151.0734	$151.07	$151.05	$151.10
Purchase #4	$246.89	3.434%	$255.3682	$255.37	$255.35	$255.40
Purchase #5	$128.72	13.778%	$146.455	$146.46	$146.45	$146.50
Purchase #6	$49.83	12.226%	$55.9222	$55.92	$55.90	$55.90
Purchase #7	$166.62	6.171%	$176.9021	$176.90	$176.90	$176.90
7 purchase totals =	$980.90		$1,047.5910	$1,047.59	$1,047.50	$1,047.60