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	$210.53	9.640%	$230.8251	$230.83	$230.85	$230.80
Purchase #2	$205.61	5.234%	$216.3716	$216.37	$216.35	$216.40
Purchase #3	$91.30	3.573%	$94.5621	$94.56	$94.55	$94.60
Purchase #4	$10.91	12.741%	$12.3	$12.30	$12.30	$12.30
Purchase #5	$88.53	6.380%	$94.1782	$94.18	$94.20	$94.20
Purchase #6	$90.46	10.596%	$100.0451	$100.05	$100.05	$100.00
Purchase #7	$40.47	13.810%	$46.0589	$46.06	$46.05	$46.10
7 purchase totals =	$737.81		$794.3410	$794.35	$794.35	$794.40