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	$86.79	12.371%	$97.5268	$97.53	$97.55	$97.50
Purchase #2	$212.96	8.695%	$231.4769	$231.48	$231.50	$231.50
Purchase #3	$78.43	5.107%	$82.4354	$82.44	$82.45	$82.40
Purchase #4	$69.30	12.828%	$78.1898	$78.19	$78.20	$78.20
Purchase #5	$129.58	7.134%	$138.8242	$138.82	$138.80	$138.80
Purchase #6	$96.35	7.511%	$103.5868	$103.59	$103.60	$103.60
Purchase #7	$134.94	11.252%	$150.1234	$150.12	$150.10	$150.10
7 purchase totals =	$808.35		$882.1633	$882.17	$882.20	$882.10