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	$81.70	4.438%	$85.3258	$85.33	$85.35	$85.30
Purchase #2	$99.31	9.221%	$108.4674	$108.47	$108.45	$108.50
Purchase #3	$154.27	10.728%	$170.8201	$170.82	$170.80	$170.80
Purchase #4	$196.55	9.653%	$215.523	$215.52	$215.50	$215.50
Purchase #5	$56.81	5.580%	$59.98	$59.98	$60.00	$60.00
Purchase #6	$33.99	6.749%	$36.284	$36.28	$36.30	$36.30
Purchase #7	$32.27	13.299%	$36.5616	$36.56	$36.55	$36.60
7 purchase totals =	$654.90		$712.9619	$712.96	$712.95	$713.00