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	$57.78	12.822%	$65.1886	$65.19	$65.20	$65.20
Purchase #2	$77.95	6.421%	$82.9552	$82.96	$82.95	$83.00
Purchase #3	$84.45	6.682%	$90.0929	$90.09	$90.10	$90.10
Purchase #4	$73.77	12.382%	$82.9042	$82.90	$82.90	$82.90
Purchase #5	$175.63	11.703%	$196.184	$196.18	$196.20	$196.20
Purchase #6	$132.83	13.201%	$150.3649	$150.36	$150.35	$150.40
Purchase #7	$200.31	5.837%	$212.0021	$212.00	$212.00	$212.00
7 purchase totals =	$802.72		$879.6919	$879.68	$879.70	$879.80