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	$6.60	9.618%	$7.2348	$7.23	$7.25	$7.20
Purchase #2	$167.56	6.667%	$178.7312	$178.73	$178.75	$178.70
Purchase #3	$45.46	9.538%	$49.796	$49.80	$49.80	$49.80
Purchase #4	$233.67	7.523%	$251.249	$251.25	$251.25	$251.20
Purchase #5	$20.35	5.733%	$21.5167	$21.52	$21.50	$21.50
Purchase #6	$168.69	9.743%	$185.1255	$185.13	$185.15	$185.10
Purchase #7	$10.53	12.660%	$11.8631	$11.86	$11.85	$11.90
7 purchase totals =	$652.86		$705.5163	$705.52	$705.55	$705.40