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	$118.40	4.289%	$123.4782	$123.48	$123.50	$123.50
Purchase #2	$225.43	11.268%	$250.8315	$250.83	$250.85	$250.80
Purchase #3	$59.32	5.416%	$62.5328	$62.53	$62.55	$62.50
Purchase #4	$159.59	5.822%	$168.8813	$168.88	$168.90	$168.90
Purchase #5	$141.27	13.564%	$160.4319	$160.43	$160.45	$160.40
Purchase #6	$34.47	8.222%	$37.3041	$37.30	$37.30	$37.30
Purchase #7	$94.81	7.347%	$101.7757	$101.78	$101.80	$101.80
7 purchase totals =	$833.29		$905.2355	$905.23	$905.35	$905.20