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	$97.71	11.768%	$109.2085	$109.21	$109.20	$109.20
Purchase #2	$136.71	11.496%	$152.4262	$152.43	$152.45	$152.40
Purchase #3	$167.76	13.776%	$190.8706	$190.87	$190.85	$190.90
Purchase #4	$215.31	10.245%	$237.3685	$237.37	$237.35	$237.40
Purchase #5	$131.72	4.181%	$137.2272	$137.23	$137.25	$137.20
Purchase #6	$209.43	5.534%	$221.0199	$221.02	$221.00	$221.00
Purchase #7	$48.90	5.168%	$51.4272	$51.43	$51.45	$51.40
7 purchase totals =	$1,007.54		$1,099.5481	$1,099.56	$1,099.55	$1,099.50