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	$65.69	7.411%	$70.5583	$70.56	$70.55	$70.60
Purchase #2	$12.39	7.873%	$13.3655	$13.37	$13.35	$13.40
Purchase #3	$79.37	7.819%	$85.5759	$85.58	$85.60	$85.60
Purchase #4	$126.86	8.127%	$137.1699	$137.17	$137.15	$137.20
Purchase #5	$91.51	4.309%	$95.4532	$95.45	$95.45	$95.50
Purchase #6	$40.62	10.180%	$44.7551	$44.76	$44.75	$44.80
Purchase #7	$140.52	7.240%	$150.6936	$150.69	$150.70	$150.70
7 purchase totals =	$556.96		$597.5715	$597.58	$597.55	$597.80