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	$33.39	12.774%	$37.6552	$37.66	$37.65	$37.70
Purchase #2	$59.33	6.443%	$63.1526	$63.15	$63.15	$63.20
Purchase #3	$200.52	12.169%	$224.9213	$224.92	$224.90	$224.90
Purchase #4	$171.27	11.425%	$190.8376	$190.84	$190.85	$190.80
Purchase #5	$146.40	12.615%	$164.8684	$164.87	$164.85	$164.90
Purchase #6	$21.61	4.485%	$22.5792	$22.58	$22.60	$22.60
Purchase #7	$165.73	3.739%	$171.9266	$171.93	$171.95	$171.90
7 purchase totals =	$798.25		$875.9409	$875.95	$875.95	$876.00