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	$63.94	4.321%	$66.7028	$66.70	$66.70	$66.70
Purchase #2	$97.61	7.476%	$104.9073	$104.91	$104.90	$104.90
Purchase #3	$144.52	5.832%	$152.9484	$152.95	$152.95	$152.90
Purchase #4	$196.65	6.681%	$209.7882	$209.79	$209.80	$209.80
Purchase #5	$233.38	11.312%	$259.7799	$259.78	$259.80	$259.80
Purchase #6	$83.32	6.477%	$88.7166	$88.72	$88.70	$88.70
Purchase #7	$143.70	3.475%	$148.6936	$148.69	$148.70	$148.70
7 purchase totals =	$963.12		$1,031.5368	$1,031.54	$1,031.55	$1,031.50