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	$87.40	4.855%	$91.6433	$91.64	$91.65	$91.60
Purchase #2	$197.57	3.555%	$204.5936	$204.59	$204.60	$204.60
Purchase #3	$119.96	5.408%	$126.4474	$126.45	$126.45	$126.40
Purchase #4	$51.74	9.257%	$56.5296	$56.53	$56.55	$56.50
Purchase #5	$72.89	7.766%	$78.5506	$78.55	$78.55	$78.60
Purchase #6	$220.70	12.262%	$247.7622	$247.76	$247.75	$247.80
Purchase #7	$57.29	3.164%	$59.1027	$59.10	$59.10	$59.10
7 purchase totals =	$807.55		$864.6294	$864.62	$864.65	$864.60