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	$56.28	11.437%	$62.7167	$62.72	$62.70	$62.70
Purchase #2	$17.78	9.505%	$19.47	$19.47	$19.45	$19.50
Purchase #3	$80.62	12.315%	$90.5484	$90.55	$90.55	$90.50
Purchase #4	$55.37	10.556%	$61.2149	$61.21	$61.20	$61.20
Purchase #5	$224.34	7.754%	$241.7353	$241.74	$241.75	$241.70
Purchase #6	$138.29	7.742%	$148.9964	$149.00	$149.00	$149.00
Purchase #7	$39.57	9.173%	$43.1998	$43.20	$43.20	$43.20
7 purchase totals =	$612.25		$667.8815	$667.89	$667.85	$667.80