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	$240.70	7.409%	$258.5335	$258.53	$258.55	$258.50
Purchase #2	$44.39	13.274%	$50.2823	$50.28	$50.30	$50.30
Purchase #3	$140.59	7.633%	$151.3212	$151.32	$151.30	$151.30
Purchase #4	$56.33	9.418%	$61.6352	$61.64	$61.65	$61.60
Purchase #5	$219.90	6.868%	$235.0027	$235.00	$235.00	$235.00
Purchase #6	$244.61	4.760%	$256.2534	$256.25	$256.25	$256.30
Purchase #7	$112.62	6.452%	$119.8862	$119.89	$119.90	$119.90
7 purchase totals =	$1,059.14		$1,132.9145	$1,132.91	$1,132.95	$1,132.90