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	$14.77	4.653%	$15.4572	$15.46	$15.45	$15.50
Purchase #2	$77.72	8.345%	$84.2057	$84.21	$84.20	$84.20
Purchase #3	$131.89	7.628%	$141.9506	$141.95	$141.95	$142.00
Purchase #4	$13.84	7.503%	$14.8784	$14.88	$14.90	$14.90
Purchase #5	$239.26	13.647%	$271.9118	$271.91	$271.90	$271.90
Purchase #6	$77.33	6.642%	$82.4663	$82.47	$82.45	$82.50
Purchase #7	$37.73	13.515%	$42.8292	$42.83	$42.85	$42.80
7 purchase totals =	$592.54		$653.6992	$653.71	$653.70	$653.80