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	$68.27	6.775%	$72.8953	$72.90	$72.90	$72.90
Purchase #2	$160.42	5.130%	$168.6495	$168.65	$168.65	$168.60
Purchase #3	$54.79	8.516%	$59.4559	$59.46	$59.45	$59.50
Purchase #4	$45.87	13.810%	$52.2046	$52.20	$52.20	$52.20
Purchase #5	$47.64	4.725%	$49.891	$49.89	$49.90	$49.90
Purchase #6	$248.51	12.463%	$279.4818	$279.48	$279.50	$279.50
Purchase #7	$65.90	6.391%	$70.1117	$70.11	$70.10	$70.10
7 purchase totals =	$691.40		$752.6898	$752.69	$752.70	$752.70