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	$236.93	4.615%	$247.8643	$247.86	$247.85	$247.90
Purchase #2	$65.35	6.184%	$69.3912	$69.39	$69.40	$69.40
Purchase #3	$99.67	11.390%	$111.0224	$111.02	$111.00	$111.00
Purchase #4	$69.47	9.545%	$76.1009	$76.10	$76.10	$76.10
Purchase #5	$242.39	7.677%	$260.9983	$261.00	$261.00	$261.00
Purchase #6	$249.93	13.859%	$284.5678	$284.57	$284.55	$284.60
Purchase #7	$100.78	10.781%	$111.6451	$111.65	$111.65	$111.60
7 purchase totals =	$1,064.52		$1,161.5900	$1,161.59	$1,161.55	$1,161.60