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	$174.79	12.644%	$196.8904	$196.89	$196.90	$196.90
Purchase #2	$155.40	12.794%	$175.2819	$175.28	$175.30	$175.30
Purchase #3	$40.79	5.210%	$42.9152	$42.92	$42.90	$42.90
Purchase #4	$46.89	12.626%	$52.8103	$52.81	$52.80	$52.80
Purchase #5	$120.27	4.142%	$125.2516	$125.25	$125.25	$125.30
Purchase #6	$250.93	12.570%	$282.4719	$282.47	$282.45	$282.50
Purchase #7	$244.66	7.224%	$262.3342	$262.33	$262.35	$262.30
7 purchase totals =	$1,033.73		$1,137.9555	$1,137.95	$1,137.95	$1,138.00