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	$182.84	12.585%	$205.8504	$205.85	$205.85	$205.90
Purchase #2	$45.37	11.845%	$50.7441	$50.74	$50.75	$50.70
Purchase #3	$37.33	11.847%	$41.7525	$41.75	$41.75	$41.80
Purchase #4	$82.73	8.595%	$89.8406	$89.84	$89.85	$89.80
Purchase #5	$41.84	9.150%	$45.6684	$45.67	$45.65	$45.70
Purchase #6	$230.56	7.418%	$247.6629	$247.66	$247.65	$247.70
Purchase #7	$202.61	11.188%	$225.278	$225.28	$225.30	$225.30
7 purchase totals =	$823.28		$906.7969	$906.79	$906.80	$906.90