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	$150.29	5.431%	$158.4522	$158.45	$158.45	$158.50
Purchase #2	$68.69	9.808%	$75.4271	$75.43	$75.45	$75.40
Purchase #3	$47.68	9.418%	$52.1705	$52.17	$52.15	$52.20
Purchase #4	$220.95	13.619%	$251.0412	$251.04	$251.05	$251.00
Purchase #5	$123.90	6.239%	$131.6301	$131.63	$131.65	$131.60
Purchase #6	$168.31	6.339%	$178.9792	$178.98	$179.00	$179.00
Purchase #7	$203.50	9.321%	$222.4682	$222.47	$222.45	$222.50
7 purchase totals =	$983.32		$1,070.1685	$1,070.17	$1,070.20	$1,070.20