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	$213.74	10.265%	$235.6804	$235.68	$235.70	$235.70
Purchase #2	$86.86	4.490%	$90.76	$90.76	$90.75	$90.80
Purchase #3	$223.62	9.524%	$244.9176	$244.92	$244.90	$244.90
Purchase #4	$64.37	12.715%	$72.5546	$72.55	$72.55	$72.60
Purchase #5	$53.90	9.528%	$59.0356	$59.04	$59.05	$59.00
Purchase #6	$83.40	13.852%	$94.9526	$94.95	$94.95	$95.00
Purchase #7	$53.51	13.568%	$60.7702	$60.77	$60.75	$60.80
7 purchase totals =	$779.40		$858.6710	$858.67	$858.65	$858.80