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	$114.69	4.133%	$119.4301	$119.43	$119.45	$119.40
Purchase #2	$215.49	8.730%	$234.3023	$234.30	$234.30	$234.30
Purchase #3	$192.65	10.830%	$213.514	$213.51	$213.50	$213.50
Purchase #4	$67.29	13.131%	$76.1258	$76.13	$76.15	$76.10
Purchase #5	$64.89	11.566%	$72.3952	$72.40	$72.40	$72.40
Purchase #6	$243.41	13.207%	$275.5572	$275.56	$275.55	$275.60
Purchase #7	$131.62	12.868%	$148.5569	$148.56	$148.55	$148.60
7 purchase totals =	$1,030.04		$1,139.8815	$1,139.89	$1,139.90	$1,139.90