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	$221.68	7.117%	$237.457	$237.46	$237.45	$237.50
Purchase #2	$44.79	6.241%	$47.5853	$47.59	$47.60	$47.60
Purchase #3	$240.80	5.212%	$253.3505	$253.35	$253.35	$253.40
Purchase #4	$94.69	11.550%	$105.6267	$105.63	$105.65	$105.60
Purchase #5	$36.45	8.814%	$39.6627	$39.66	$39.65	$39.70
Purchase #6	$52.66	3.168%	$54.3283	$54.33	$54.35	$54.30
Purchase #7	$244.26	12.530%	$274.8658	$274.87	$274.85	$274.90
7 purchase totals =	$935.33		$1,012.8763	$1,012.89	$1,012.90	$1,013.00