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	$210.73	3.386%	$217.8653	$217.87	$217.85	$217.90
Purchase #2	$82.30	4.210%	$85.7648	$85.76	$85.75	$85.80
Purchase #3	$37.52	12.221%	$42.1053	$42.11	$42.10	$42.10
Purchase #4	$145.69	3.517%	$150.8139	$150.81	$150.80	$150.80
Purchase #5	$46.61	3.453%	$48.2194	$48.22	$48.20	$48.20
Purchase #6	$133.95	7.682%	$144.24	$144.24	$144.25	$144.20
Purchase #7	$11.74	3.249%	$12.1214	$12.12	$12.10	$12.10
7 purchase totals =	$668.54		$701.1301	$701.13	$701.05	$701.10