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	$127.85	3.216%	$131.9617	$131.96	$131.95	$132.00
Purchase #2	$124.78	10.508%	$137.8919	$137.89	$137.90	$137.90
Purchase #3	$93.60	13.366%	$106.1106	$106.11	$106.10	$106.10
Purchase #4	$29.78	12.545%	$33.5159	$33.52	$33.50	$33.50
Purchase #5	$103.44	11.216%	$115.0418	$115.04	$115.05	$115.00
Purchase #6	$224.45	13.225%	$254.1335	$254.13	$254.15	$254.10
Purchase #7	$84.46	6.855%	$90.2497	$90.25	$90.25	$90.20
7 purchase totals =	$788.36		$868.9051	$868.90	$868.90	$868.80