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	$95.32	10.703%	$105.5221	$105.52	$105.50	$105.50
Purchase #2	$200.65	11.868%	$224.4631	$224.46	$224.45	$224.50
Purchase #3	$156.50	12.317%	$175.7761	$175.78	$175.80	$175.80
Purchase #4	$130.86	7.744%	$140.9938	$140.99	$141.00	$141.00
Purchase #5	$248.90	8.259%	$269.4567	$269.46	$269.45	$269.50
Purchase #6	$181.50	8.513%	$196.9511	$196.95	$196.95	$197.00
Purchase #7	$219.52	11.349%	$244.4333	$244.43	$244.45	$244.40
7 purchase totals =	$1,233.25		$1,357.5962	$1,357.59	$1,357.60	$1,357.70