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	$42.73	12.507%	$48.0742	$48.07	$48.05	$48.10
Purchase #2	$37.85	6.651%	$40.3674	$40.37	$40.35	$40.40
Purchase #3	$139.26	6.793%	$148.7199	$148.72	$148.70	$148.70
Purchase #4	$29.59	7.831%	$31.9072	$31.91	$31.90	$31.90
Purchase #5	$7.99	10.438%	$8.824	$8.82	$8.80	$8.80
Purchase #6	$118.45	10.856%	$131.3089	$131.31	$131.30	$131.30
Purchase #7	$47.77	6.631%	$50.9376	$50.94	$50.95	$50.90
7 purchase totals =	$423.64		$460.1392	$460.14	$460.05	$460.10