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	$225.52	9.701%	$247.3977	$247.40	$247.40	$247.40
Purchase #2	$70.90	10.687%	$78.4771	$78.48	$78.50	$78.50
Purchase #3	$37.25	12.142%	$41.7729	$41.77	$41.75	$41.80
Purchase #4	$186.69	10.282%	$205.8855	$205.89	$205.90	$205.90
Purchase #5	$221.87	5.371%	$233.7866	$233.79	$233.80	$233.80
Purchase #6	$235.81	13.516%	$267.6821	$267.68	$267.70	$267.70
Purchase #7	$196.45	11.554%	$219.1478	$219.15	$219.15	$219.10
7 purchase totals =	$1,174.49		$1,294.1497	$1,294.16	$1,294.20	$1,294.20