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	$187.48	6.746%	$200.1274	$200.13	$200.15	$200.10
Purchase #2	$83.88	4.749%	$87.8635	$87.86	$87.85	$87.90
Purchase #3	$166.99	10.485%	$184.4989	$184.50	$184.50	$184.50
Purchase #4	$170.48	3.440%	$176.3445	$176.34	$176.35	$176.30
Purchase #5	$244.65	8.225%	$264.7725	$264.77	$264.75	$264.80
Purchase #6	$125.84	13.313%	$142.5931	$142.59	$142.60	$142.60
Purchase #7	$82.82	4.702%	$86.7142	$86.71	$86.70	$86.70
7 purchase totals =	$1,062.14		$1,142.9141	$1,142.90	$1,142.90	$1,142.90