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	$242.86	7.621%	$261.3684	$261.37	$261.35	$261.40
Purchase #2	$248.60	10.224%	$274.0169	$274.02	$274.00	$274.00
Purchase #3	$7.36	3.421%	$7.6118	$7.61	$7.60	$7.60
Purchase #4	$178.39	5.621%	$188.4173	$188.42	$188.40	$188.40
Purchase #5	$215.47	3.202%	$222.3693	$222.37	$222.35	$222.40
Purchase #6	$158.36	12.643%	$178.3815	$178.38	$178.40	$178.40
Purchase #7	$178.63	12.503%	$200.9641	$200.96	$200.95	$201.00
7 purchase totals =	$1,229.67		$1,333.1293	$1,333.13	$1,333.05	$1,333.20