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	$31.33	7.201%	$33.5861	$33.59	$33.60	$33.60
Purchase #2	$191.45	11.344%	$213.1681	$213.17	$213.15	$213.20
Purchase #3	$191.32	11.113%	$212.5814	$212.58	$212.60	$212.60
Purchase #4	$64.90	10.554%	$71.7495	$71.75	$71.75	$71.70
Purchase #5	$40.56	3.599%	$42.0198	$42.02	$42.00	$42.00
Purchase #6	$12.43	10.637%	$13.7522	$13.75	$13.75	$13.80
Purchase #7	$36.36	4.409%	$37.9631	$37.96	$37.95	$38.00
7 purchase totals =	$568.35		$624.8202	$624.82	$624.80	$624.90