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	$239.88	13.214%	$271.5777	$271.58	$271.60	$271.60
Purchase #2	$76.46	7.651%	$82.31	$82.31	$82.30	$82.30
Purchase #3	$86.95	5.197%	$91.4688	$91.47	$91.45	$91.50
Purchase #4	$149.79	4.870%	$157.0848	$157.08	$157.10	$157.10
Purchase #5	$145.37	4.795%	$152.3405	$152.34	$152.35	$152.30
Purchase #6	$197.31	13.195%	$223.3451	$223.35	$223.35	$223.30
Purchase #7	$151.34	12.695%	$170.5526	$170.55	$170.55	$170.60
7 purchase totals =	$1,047.10		$1,148.6795	$1,148.68	$1,148.70	$1,148.70