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	$209.59	7.793%	$225.9233	$225.92	$225.90	$225.90
Purchase #2	$198.73	13.639%	$225.8348	$225.83	$225.85	$225.80
Purchase #3	$26.69	6.355%	$28.3861	$28.39	$28.40	$28.40
Purchase #4	$65.84	8.532%	$71.4575	$71.46	$71.45	$71.50
Purchase #5	$109.80	5.660%	$116.0147	$116.01	$116.00	$116.00
Purchase #6	$175.26	3.667%	$181.6868	$181.69	$181.70	$181.70
Purchase #7	$217.90	13.330%	$246.9461	$246.95	$246.95	$246.90
7 purchase totals =	$1,003.81		$1,096.2493	$1,096.25	$1,096.25	$1,096.20