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	$63.80	12.749%	$71.9339	$71.93	$71.95	$71.90
Purchase #2	$43.50	10.667%	$48.1401	$48.14	$48.15	$48.10
Purchase #3	$67.79	13.477%	$76.9261	$76.93	$76.95	$76.90
Purchase #4	$71.63	7.323%	$76.8755	$76.88	$76.90	$76.90
Purchase #5	$129.54	9.392%	$141.7064	$141.71	$141.70	$141.70
Purchase #6	$182.95	7.472%	$196.62	$196.62	$196.60	$196.60
Purchase #7	$158.75	13.137%	$179.605	$179.61	$179.60	$179.60
7 purchase totals =	$717.96		$791.8070	$791.82	$791.85	$791.70