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	$83.99	7.533%	$90.317	$90.32	$90.30	$90.30
Purchase #2	$173.82	10.589%	$192.2258	$192.23	$192.25	$192.20
Purchase #3	$15.86	10.558%	$17.5345	$17.53	$17.55	$17.50
Purchase #4	$89.95	4.579%	$94.0688	$94.07	$94.05	$94.10
Purchase #5	$205.61	3.612%	$213.0366	$213.04	$213.05	$213.00
Purchase #6	$103.57	5.486%	$109.2519	$109.25	$109.25	$109.30
Purchase #7	$149.76	10.396%	$165.329	$165.33	$165.35	$165.30
7 purchase totals =	$822.56		$881.7636	$881.77	$881.80	$881.70