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	$84.69	13.582%	$96.1926	$96.19	$96.20	$96.20
Purchase #2	$181.90	5.641%	$192.161	$192.16	$192.15	$192.20
Purchase #3	$100.96	13.375%	$114.4634	$114.46	$114.45	$114.50
Purchase #4	$177.56	8.633%	$192.8888	$192.89	$192.90	$192.90
Purchase #5	$79.88	3.824%	$82.9346	$82.93	$82.95	$82.90
Purchase #6	$155.72	10.270%	$171.7124	$171.71	$171.70	$171.70
Purchase #7	$89.39	13.727%	$101.6606	$101.66	$101.65	$101.70
7 purchase totals =	$870.10		$952.0134	$952.00	$952.00	$952.10