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	$191.68	6.174%	$203.5143	$203.51	$203.50	$203.50
Purchase #2	$160.65	6.752%	$171.4971	$171.50	$171.50	$171.50
Purchase #3	$41.45	10.808%	$45.9299	$45.93	$45.95	$45.90
Purchase #4	$72.90	7.784%	$78.5745	$78.57	$78.55	$78.60
Purchase #5	$227.64	12.590%	$256.2999	$256.30	$256.30	$256.30
Purchase #6	$31.54	6.193%	$33.4933	$33.49	$33.50	$33.50
Purchase #7	$73.76	3.211%	$76.1284	$76.13	$76.15	$76.10
7 purchase totals =	$799.62		$865.4374	$865.43	$865.45	$865.40