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	$112.53	11.847%	$125.8614	$125.86	$125.85	$125.90
Purchase #2	$94.40	6.792%	$100.8116	$100.81	$100.80	$100.80
Purchase #3	$78.90	5.771%	$83.4533	$83.45	$83.45	$83.50
Purchase #4	$57.79	6.164%	$61.3522	$61.35	$61.35	$61.40
Purchase #5	$70.39	11.528%	$78.5046	$78.50	$78.50	$78.50
Purchase #6	$151.54	3.268%	$156.4923	$156.49	$156.50	$156.50
Purchase #7	$152.66	4.605%	$159.69	$159.69	$159.70	$159.70
7 purchase totals =	$718.21		$766.1654	$766.15	$766.15	$766.30