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	$37.56	8.298%	$40.6767	$40.68	$40.70	$40.70
Purchase #2	$196.49	6.734%	$209.7216	$209.72	$209.70	$209.70
Purchase #3	$141.56	3.675%	$146.7623	$146.76	$146.75	$146.80
Purchase #4	$202.39	11.678%	$226.0251	$226.03	$226.05	$226.00
Purchase #5	$94.90	9.797%	$104.1974	$104.20	$104.20	$104.20
Purchase #6	$246.44	13.409%	$279.4851	$279.49	$279.50	$279.50
Purchase #7	$48.42	12.150%	$54.303	$54.30	$54.30	$54.30
7 purchase totals =	$967.76		$1,061.1712	$1,061.18	$1,061.20	$1,061.20