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	$95.59	4.426%	$99.8208	$99.82	$99.80	$99.80
Purchase #2	$65.69	10.787%	$72.776	$72.78	$72.80	$72.80
Purchase #3	$64.82	10.687%	$71.7473	$71.75	$71.75	$71.70
Purchase #4	$20.28	11.405%	$22.5929	$22.59	$22.60	$22.60
Purchase #5	$152.82	5.669%	$161.4834	$161.48	$161.50	$161.50
Purchase #6	$148.74	5.684%	$157.1944	$157.19	$157.20	$157.20
Purchase #7	$40.36	4.646%	$42.2351	$42.24	$42.25	$42.20
7 purchase totals =	$588.30		$627.8499	$627.85	$627.90	$627.80