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	$10.61	8.794%	$11.543	$11.54	$11.55	$11.50
Purchase #2	$98.70	12.478%	$111.0158	$111.02	$111.00	$111.00
Purchase #3	$147.66	13.797%	$168.0327	$168.03	$168.05	$168.00
Purchase #4	$184.30	3.338%	$190.4519	$190.45	$190.45	$190.50
Purchase #5	$173.53	13.481%	$196.9236	$196.92	$196.90	$196.90
Purchase #6	$46.63	8.484%	$50.5861	$50.59	$50.60	$50.60
Purchase #7	$135.57	8.313%	$146.8399	$146.84	$146.85	$146.80
7 purchase totals =	$797.00		$875.3930	$875.39	$875.40	$875.30