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	$183.95	3.418%	$190.2374	$190.24	$190.25	$190.20
Purchase #2	$30.82	8.659%	$33.4887	$33.49	$33.50	$33.50
Purchase #3	$39.56	8.539%	$42.938	$42.94	$42.95	$42.90
Purchase #4	$166.94	4.327%	$174.1635	$174.16	$174.15	$174.20
Purchase #5	$26.48	11.668%	$29.5697	$29.57	$29.55	$29.60
Purchase #6	$61.50	9.843%	$67.5534	$67.55	$67.55	$67.60
Purchase #7	$85.67	5.791%	$90.6311	$90.63	$90.65	$90.60
7 purchase totals =	$594.92		$628.5818	$628.58	$628.60	$628.60