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	$31.52	3.711%	$32.6897	$32.69	$32.70	$32.70
Purchase #2	$44.99	7.616%	$48.4164	$48.42	$48.40	$48.40
Purchase #3	$83.77	7.771%	$90.2798	$90.28	$90.30	$90.30
Purchase #4	$27.95	11.530%	$31.1726	$31.17	$31.15	$31.20
Purchase #5	$215.85	8.329%	$233.8281	$233.83	$233.85	$233.80
Purchase #6	$114.72	8.715%	$124.7178	$124.72	$124.70	$124.70
Purchase #7	$185.27	6.513%	$197.3366	$197.34	$197.35	$197.30
7 purchase totals =	$704.07		$758.4410	$758.45	$758.45	$758.40