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	$222.76	7.240%	$238.8878	$238.89	$238.90	$238.90
Purchase #2	$82.85	8.545%	$89.9295	$89.93	$89.95	$89.90
Purchase #3	$7.34	4.799%	$7.6922	$7.69	$7.70	$7.70
Purchase #4	$162.51	10.586%	$179.7133	$179.71	$179.70	$179.70
Purchase #5	$82.64	6.361%	$87.8967	$87.90	$87.90	$87.90
Purchase #6	$112.40	3.492%	$116.325	$116.33	$116.35	$116.30
Purchase #7	$24.88	5.313%	$26.2019	$26.20	$26.20	$26.20
7 purchase totals =	$695.38		$746.6464	$746.65	$746.70	$746.60