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	$150.41	4.445%	$157.0957	$157.10	$157.10	$157.10
Purchase #2	$29.97	4.472%	$31.3103	$31.31	$31.30	$31.30
Purchase #3	$64.72	3.683%	$67.1036	$67.10	$67.10	$67.10
Purchase #4	$233.53	13.477%	$265.0028	$265.00	$265.00	$265.00
Purchase #5	$213.49	13.672%	$242.6784	$242.68	$242.70	$242.70
Purchase #6	$114.72	7.406%	$123.2162	$123.22	$123.20	$123.20
Purchase #7	$137.54	10.102%	$151.4343	$151.43	$151.45	$151.40
7 purchase totals =	$944.38		$1,037.8413	$1,037.84	$1,037.85	$1,037.80