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	$202.31	11.738%	$226.0571	$226.06	$226.05	$226.10
Purchase #2	$149.28	12.767%	$168.3386	$168.34	$168.35	$168.30
Purchase #3	$59.72	10.271%	$65.8538	$65.85	$65.85	$65.90
Purchase #4	$123.79	12.211%	$138.906	$138.91	$138.90	$138.90
Purchase #5	$240.59	6.776%	$256.8924	$256.89	$256.90	$256.90
Purchase #6	$49.53	9.485%	$54.2279	$54.23	$54.25	$54.20
Purchase #7	$11.68	11.465%	$13.0191	$13.02	$13.00	$13.00
7 purchase totals =	$836.90		$923.2949	$923.30	$923.30	$923.30