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	$121.34	8.764%	$131.9742	$131.97	$131.95	$132.00
Purchase #2	$53.47	7.174%	$57.3059	$57.31	$57.30	$57.30
Purchase #3	$118.86	9.873%	$130.595	$130.60	$130.60	$130.60
Purchase #4	$29.83	7.452%	$32.0529	$32.05	$32.05	$32.10
Purchase #5	$115.32	4.869%	$120.9349	$120.93	$120.95	$120.90
Purchase #6	$28.31	4.206%	$29.5007	$29.50	$29.50	$29.50
Purchase #7	$172.66	7.519%	$185.6423	$185.64	$185.65	$185.60
7 purchase totals =	$639.79		$688.0059	$688.00	$688.00	$688.00