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	$77.76	10.413%	$85.8571	$85.86	$85.85	$85.90
Purchase #2	$30.56	9.150%	$33.3562	$33.36	$33.35	$33.40
Purchase #3	$156.38	8.482%	$169.6442	$169.64	$169.65	$169.60
Purchase #4	$66.68	8.522%	$72.3625	$72.36	$72.35	$72.40
Purchase #5	$132.89	6.559%	$141.6063	$141.61	$141.60	$141.60
Purchase #6	$51.75	4.393%	$54.0234	$54.02	$54.00	$54.00
Purchase #7	$188.90	4.167%	$196.7715	$196.77	$196.75	$196.80
7 purchase totals =	$704.92		$753.6212	$753.62	$753.55	$753.70