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	$83.53	9.661%	$91.5998	$91.60	$91.60	$91.60
Purchase #2	$99.34	10.160%	$109.4329	$109.43	$109.45	$109.40
Purchase #3	$237.53	4.234%	$247.587	$247.59	$247.60	$247.60
Purchase #4	$65.39	7.494%	$70.2903	$70.29	$70.30	$70.30
Purchase #5	$75.66	13.342%	$85.7546	$85.75	$85.75	$85.80
Purchase #6	$86.60	12.102%	$97.0803	$97.08	$97.10	$97.10
Purchase #7	$53.46	11.312%	$59.5074	$59.51	$59.50	$59.50
7 purchase totals =	$701.51		$761.2523	$761.25	$761.30	$761.30