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	$235.66	3.803%	$244.6221	$244.62	$244.60	$244.60
Purchase #2	$42.93	7.206%	$46.0235	$46.02	$46.00	$46.00
Purchase #3	$39.74	13.307%	$45.0282	$45.03	$45.05	$45.00
Purchase #4	$208.43	4.836%	$218.5097	$218.51	$218.50	$218.50
Purchase #5	$76.67	11.834%	$85.7431	$85.74	$85.75	$85.70
Purchase #6	$131.54	8.208%	$142.3368	$142.34	$142.35	$142.30
Purchase #7	$37.64	6.377%	$40.0403	$40.04	$40.05	$40.00
7 purchase totals =	$772.61		$822.3037	$822.30	$822.30	$822.10