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	$30.64	3.456%	$31.6989	$31.70	$31.70	$31.70
Purchase #2	$36.28	4.519%	$37.9195	$37.92	$37.90	$37.90
Purchase #3	$185.34	12.710%	$208.8967	$208.90	$208.90	$208.90
Purchase #4	$131.35	8.208%	$142.1312	$142.13	$142.15	$142.10
Purchase #5	$43.85	11.541%	$48.9107	$48.91	$48.90	$48.90
Purchase #6	$200.78	9.182%	$219.2156	$219.22	$219.20	$219.20
Purchase #7	$169.72	11.281%	$188.8661	$188.87	$188.85	$188.90
7 purchase totals =	$797.96		$877.6387	$877.65	$877.60	$877.60