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	$217.36	3.686%	$225.3719	$225.37	$225.35	$225.40
Purchase #2	$161.93	9.637%	$177.5352	$177.54	$177.55	$177.50
Purchase #3	$245.90	3.753%	$255.1286	$255.13	$255.15	$255.10
Purchase #4	$93.68	6.856%	$100.1027	$100.10	$100.10	$100.10
Purchase #5	$42.83	6.178%	$45.476	$45.48	$45.50	$45.50
Purchase #6	$152.80	13.334%	$173.1744	$173.17	$173.15	$173.20
Purchase #7	$205.64	5.859%	$217.6884	$217.69	$217.70	$217.70
7 purchase totals =	$1,120.14		$1,194.4772	$1,194.48	$1,194.50	$1,194.50