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	$52.87	7.375%	$56.7692	$56.77	$56.75	$56.80
Purchase #2	$149.51	8.456%	$162.1526	$162.15	$162.15	$162.20
Purchase #3	$6.94	13.741%	$7.8936	$7.89	$7.90	$7.90
Purchase #4	$146.60	4.298%	$152.9009	$152.90	$152.90	$152.90
Purchase #5	$61.87	7.695%	$66.6309	$66.63	$66.65	$66.60
Purchase #6	$215.53	8.451%	$233.7444	$233.74	$233.75	$233.70
Purchase #7	$227.31	4.767%	$238.1459	$238.15	$238.15	$238.10
7 purchase totals =	$860.63		$918.2375	$918.23	$918.25	$918.20