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	$239.50	5.165%	$251.8702	$251.87	$251.85	$251.90
Purchase #2	$26.88	5.711%	$28.4151	$28.42	$28.40	$28.40
Purchase #3	$146.35	5.409%	$154.2661	$154.27	$154.25	$154.30
Purchase #4	$177.80	6.302%	$189.005	$189.01	$189.00	$189.00
Purchase #5	$140.34	11.745%	$156.8229	$156.82	$156.80	$156.80
Purchase #6	$46.30	12.567%	$52.1185	$52.12	$52.10	$52.10
Purchase #7	$233.42	8.834%	$254.0403	$254.04	$254.05	$254.00
7 purchase totals =	$1,010.59		$1,086.5381	$1,086.55	$1,086.45	$1,086.50