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	$212.69	11.539%	$237.2323	$237.23	$237.25	$237.20
Purchase #2	$82.60	8.578%	$89.6854	$89.69	$89.70	$89.70
Purchase #3	$248.61	12.639%	$280.0318	$280.03	$280.05	$280.00
Purchase #4	$139.32	9.131%	$152.0413	$152.04	$152.05	$152.00
Purchase #5	$219.27	12.653%	$247.0142	$247.01	$247.00	$247.00
Purchase #6	$29.56	7.695%	$31.8346	$31.83	$31.85	$31.80
Purchase #7	$129.39	12.161%	$145.1251	$145.13	$145.15	$145.10
7 purchase totals =	$1,061.44		$1,182.9647	$1,182.96	$1,183.05	$1,182.80