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	$39.52	4.509%	$41.302	$41.30	$41.30	$41.30
Purchase #2	$39.58	7.525%	$42.5584	$42.56	$42.55	$42.60
Purchase #3	$19.95	3.481%	$20.6445	$20.64	$20.65	$20.60
Purchase #4	$165.47	4.417%	$172.7788	$172.78	$172.80	$172.80
Purchase #5	$244.81	3.322%	$252.9426	$252.94	$252.95	$252.90
Purchase #6	$232.58	4.594%	$243.2647	$243.26	$243.25	$243.30
Purchase #7	$240.50	9.803%	$264.0762	$264.08	$264.10	$264.10
7 purchase totals =	$982.41		$1,037.5672	$1,037.56	$1,037.60	$1,037.60