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	$221.29	9.642%	$242.6268	$242.63	$242.65	$242.60
Purchase #2	$125.94	4.120%	$131.1287	$131.13	$131.15	$131.10
Purchase #3	$158.39	6.444%	$168.5967	$168.60	$168.60	$168.60
Purchase #4	$104.53	5.709%	$110.4976	$110.50	$110.50	$110.50
Purchase #5	$54.89	9.214%	$59.9476	$59.95	$59.95	$59.90
Purchase #6	$104.64	5.754%	$110.661	$110.66	$110.65	$110.70
Purchase #7	$125.57	5.486%	$132.4588	$132.46	$132.45	$132.50
7 purchase totals =	$895.25		$955.9172	$955.93	$955.95	$955.90