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	$83.82	4.139%	$87.2893	$87.29	$87.30	$87.30
Purchase #2	$162.61	5.658%	$171.8105	$171.81	$171.80	$171.80
Purchase #3	$168.59	3.343%	$174.226	$174.23	$174.25	$174.20
Purchase #4	$50.39	8.429%	$54.6374	$54.64	$54.65	$54.60
Purchase #5	$86.33	8.224%	$93.4298	$93.43	$93.45	$93.40
Purchase #6	$114.73	7.637%	$123.4919	$123.49	$123.50	$123.50
Purchase #7	$231.71	11.756%	$258.9498	$258.95	$258.95	$258.90
7 purchase totals =	$898.18		$963.8347	$963.84	$963.90	$963.70