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	$91.49	9.125%	$99.8385	$99.84	$99.85	$99.80
Purchase #2	$202.25	8.854%	$220.1572	$220.16	$220.15	$220.20
Purchase #3	$27.56	12.611%	$31.0356	$31.04	$31.05	$31.00
Purchase #4	$216.33	11.847%	$241.9586	$241.96	$241.95	$242.00
Purchase #5	$139.55	13.845%	$158.8707	$158.87	$158.85	$158.90
Purchase #6	$226.32	6.690%	$241.4608	$241.46	$241.45	$241.50
Purchase #7	$95.70	4.603%	$100.1051	$100.11	$100.10	$100.10
7 purchase totals =	$999.20		$1,093.4265	$1,093.44	$1,093.40	$1,093.50