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	$154.98	11.714%	$173.1344	$173.13	$173.15	$173.10
Purchase #2	$179.78	11.224%	$199.9585	$199.96	$199.95	$200.00
Purchase #3	$11.54	3.370%	$11.9289	$11.93	$11.95	$11.90
Purchase #4	$29.65	12.429%	$33.3352	$33.34	$33.35	$33.30
Purchase #5	$125.30	10.149%	$138.0167	$138.02	$138.00	$138.00
Purchase #6	$78.73	13.438%	$89.3097	$89.31	$89.30	$89.30
Purchase #7	$53.60	10.676%	$59.3223	$59.32	$59.30	$59.30
7 purchase totals =	$633.58		$705.0057	$705.01	$705.00	$704.90