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	$249.46	3.494%	$258.1761	$258.18	$258.20	$258.20
Purchase #2	$121.93	3.423%	$126.1037	$126.10	$126.10	$126.10
Purchase #3	$19.85	7.795%	$21.3973	$21.40	$21.40	$21.40
Purchase #4	$190.86	3.118%	$196.811	$196.81	$196.80	$196.80
Purchase #5	$146.67	12.852%	$165.52	$165.52	$165.50	$165.50
Purchase #6	$242.71	5.579%	$256.2508	$256.25	$256.25	$256.30
Purchase #7	$206.98	7.573%	$222.6546	$222.65	$222.65	$222.70
7 purchase totals =	$1,178.46		$1,246.9135	$1,246.91	$1,246.90	$1,247.00