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	$236.44	4.455%	$246.9734	$246.97	$246.95	$247.00
Purchase #2	$104.87	6.408%	$111.5901	$111.59	$111.60	$111.60
Purchase #3	$85.85	3.158%	$88.5611	$88.56	$88.55	$88.60
Purchase #4	$28.75	8.832%	$31.2892	$31.29	$31.30	$31.30
Purchase #5	$14.65	4.135%	$15.2558	$15.26	$15.25	$15.30
Purchase #6	$60.85	10.291%	$67.1121	$67.11	$67.10	$67.10
Purchase #7	$42.89	12.601%	$48.2946	$48.29	$48.30	$48.30
7 purchase totals =	$574.30		$609.0763	$609.07	$609.05	$609.20