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	$37.44	11.666%	$41.8078	$41.81	$41.80	$41.80
Purchase #2	$38.66	6.223%	$41.0658	$41.07	$41.05	$41.10
Purchase #3	$104.50	6.362%	$111.1483	$111.15	$111.15	$111.10
Purchase #4	$158.53	5.492%	$167.2365	$167.24	$167.25	$167.20
Purchase #5	$80.76	3.574%	$83.6464	$83.65	$83.65	$83.60
Purchase #6	$135.90	5.448%	$143.3038	$143.30	$143.30	$143.30
Purchase #7	$86.88	11.341%	$96.7331	$96.73	$96.75	$96.70
7 purchase totals =	$642.67		$684.9417	$684.95	$684.95	$684.80