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	$108.41	7.641%	$116.6936	$116.69	$116.70	$116.70
Purchase #2	$42.64	6.734%	$45.5114	$45.51	$45.50	$45.50
Purchase #3	$48.98	9.199%	$53.4857	$53.49	$53.50	$53.50
Purchase #4	$75.86	9.683%	$83.2055	$83.21	$83.20	$83.20
Purchase #5	$40.74	10.492%	$45.0144	$45.01	$45.00	$45.00
Purchase #6	$77.73	4.227%	$81.0156	$81.02	$81.00	$81.00
Purchase #7	$44.29	7.314%	$47.5294	$47.53	$47.55	$47.50
7 purchase totals =	$438.65		$472.4556	$472.46	$472.45	$472.40