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	$117.60	9.440%	$128.7014	$128.70	$128.70	$128.70
Purchase #2	$235.51	3.325%	$243.3407	$243.34	$243.35	$243.30
Purchase #3	$153.61	4.147%	$159.9802	$159.98	$160.00	$160.00
Purchase #4	$192.81	4.217%	$200.9408	$200.94	$200.95	$200.90
Purchase #5	$141.58	6.820%	$151.2358	$151.24	$151.25	$151.20
Purchase #6	$141.63	6.291%	$150.5399	$150.54	$150.55	$150.50
Purchase #7	$243.48	9.135%	$265.7219	$265.72	$265.70	$265.70
7 purchase totals =	$1,226.22		$1,300.4607	$1,300.46	$1,300.50	$1,300.30