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	$238.25	11.196%	$264.9245	$264.92	$264.90	$264.90
Purchase #2	$119.41	11.600%	$133.2616	$133.26	$133.25	$133.30
Purchase #3	$219.79	12.607%	$247.4989	$247.50	$247.50	$247.50
Purchase #4	$37.35	9.595%	$40.9337	$40.93	$40.95	$40.90
Purchase #5	$75.83	10.527%	$83.8126	$83.81	$83.80	$83.80
Purchase #6	$36.92	12.179%	$41.4165	$41.42	$41.40	$41.40
Purchase #7	$96.36	8.377%	$104.4321	$104.43	$104.45	$104.40
7 purchase totals =	$823.91		$916.2799	$916.27	$916.25	$916.20