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	$59.52	6.187%	$63.2025	$63.20	$63.20	$63.20
Purchase #2	$18.75	11.206%	$20.8511	$20.85	$20.85	$20.90
Purchase #3	$131.38	13.322%	$148.8824	$148.88	$148.90	$148.90
Purchase #4	$145.65	4.853%	$152.7184	$152.72	$152.70	$152.70
Purchase #5	$215.26	3.339%	$222.4475	$222.45	$222.45	$222.40
Purchase #6	$190.71	5.346%	$200.9054	$200.91	$200.90	$200.90
Purchase #7	$112.46	6.145%	$119.3707	$119.37	$119.35	$119.40
7 purchase totals =	$873.73		$928.3780	$928.38	$928.35	$928.40