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	$103.83	10.587%	$114.8225	$114.82	$114.80	$114.80
Purchase #2	$191.97	13.831%	$218.5214	$218.52	$218.50	$218.50
Purchase #3	$157.39	5.420%	$165.9205	$165.92	$165.90	$165.90
Purchase #4	$71.77	7.275%	$76.9913	$76.99	$77.00	$77.00
Purchase #5	$56.75	5.580%	$59.9167	$59.92	$59.90	$59.90
Purchase #6	$21.49	7.231%	$23.0439	$23.04	$23.05	$23.00
Purchase #7	$38.48	10.584%	$42.5527	$42.55	$42.55	$42.60
7 purchase totals =	$641.68		$701.7690	$701.76	$701.70	$701.70