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	$227.33	10.650%	$251.5406	$251.54	$251.55	$251.50
Purchase #2	$35.50	9.460%	$38.8583	$38.86	$38.85	$38.90
Purchase #3	$143.81	12.217%	$161.3793	$161.38	$161.40	$161.40
Purchase #4	$68.85	11.710%	$76.9123	$76.91	$76.90	$76.90
Purchase #5	$148.72	13.309%	$168.5131	$168.51	$168.50	$168.50
Purchase #6	$12.49	7.171%	$13.3857	$13.39	$13.40	$13.40
Purchase #7	$227.73	5.742%	$240.8063	$240.81	$240.80	$240.80
7 purchase totals =	$864.43		$951.3956	$951.40	$951.40	$951.40