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	$162.83	3.305%	$168.2115	$168.21	$168.20	$168.20
Purchase #2	$178.39	7.433%	$191.6497	$191.65	$191.65	$191.60
Purchase #3	$93.77	9.817%	$102.9754	$102.98	$103.00	$103.00
Purchase #4	$62.89	13.511%	$71.3871	$71.39	$71.40	$71.40
Purchase #5	$144.86	5.763%	$153.2083	$153.21	$153.20	$153.20
Purchase #6	$37.70	12.711%	$42.492	$42.49	$42.50	$42.50
Purchase #7	$150.32	8.139%	$162.5545	$162.55	$162.55	$162.60
7 purchase totals =	$830.76		$892.4785	$892.48	$892.50	$892.50