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	$133.53	4.279%	$139.2437	$139.24	$139.25	$139.20
Purchase #2	$20.34	11.331%	$22.6447	$22.64	$22.65	$22.60
Purchase #3	$18.83	13.477%	$21.3677	$21.37	$21.35	$21.40
Purchase #4	$46.74	8.770%	$50.8391	$50.84	$50.85	$50.80
Purchase #5	$167.35	13.841%	$190.5129	$190.51	$190.50	$190.50
Purchase #6	$111.97	3.477%	$115.8632	$115.86	$115.85	$115.90
Purchase #7	$168.89	13.699%	$192.0262	$192.03	$192.05	$192.00
7 purchase totals =	$667.65		$732.4975	$732.49	$732.50	$732.40