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	$10.58	3.437%	$10.9436	$10.94	$10.95	$10.90
Purchase #2	$77.70	13.357%	$88.0784	$88.08	$88.10	$88.10
Purchase #3	$137.84	11.367%	$153.5083	$153.51	$153.50	$153.50
Purchase #4	$187.39	12.234%	$210.3153	$210.32	$210.30	$210.30
Purchase #5	$55.56	6.299%	$59.0597	$59.06	$59.05	$59.10
Purchase #6	$35.57	10.561%	$39.3265	$39.33	$39.35	$39.30
Purchase #7	$43.81	9.395%	$47.9259	$47.93	$47.95	$47.90
7 purchase totals =	$548.45		$609.1577	$609.17	$609.20	$609.10