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	$117.72	5.824%	$124.576	$124.58	$124.60	$124.60
Purchase #2	$130.79	6.730%	$139.5922	$139.59	$139.60	$139.60
Purchase #3	$89.63	11.869%	$100.2682	$100.27	$100.25	$100.30
Purchase #4	$24.31	10.636%	$26.8956	$26.90	$26.90	$26.90
Purchase #5	$29.80	12.396%	$33.494	$33.49	$33.50	$33.50
Purchase #6	$242.61	7.652%	$261.1745	$261.17	$261.15	$261.20
Purchase #7	$62.81	7.579%	$67.5704	$67.57	$67.55	$67.60
7 purchase totals =	$697.67		$753.5709	$753.57	$753.55	$753.70