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	$223.38	3.788%	$231.8416	$231.84	$231.85	$231.80
Purchase #2	$250.35	6.492%	$266.6027	$266.60	$266.60	$266.60
Purchase #3	$33.44	10.788%	$37.0475	$37.05	$37.05	$37.00
Purchase #4	$116.84	8.648%	$126.9443	$126.94	$126.95	$126.90
Purchase #5	$164.60	4.820%	$172.5337	$172.53	$172.55	$172.50
Purchase #6	$191.80	3.859%	$199.2016	$199.20	$199.20	$199.20
Purchase #7	$118.32	10.612%	$130.8761	$130.88	$130.90	$130.90
7 purchase totals =	$1,098.73		$1,165.0475	$1,165.04	$1,165.10	$1,164.90