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	$196.47	13.637%	$223.2626	$223.26	$223.25	$223.30
Purchase #2	$154.47	11.667%	$172.492	$172.49	$172.50	$172.50
Purchase #3	$27.63	12.630%	$31.1197	$31.12	$31.10	$31.10
Purchase #4	$239.71	8.521%	$260.1357	$260.14	$260.15	$260.10
Purchase #5	$210.99	9.610%	$231.2661	$231.27	$231.25	$231.30
Purchase #6	$78.73	13.511%	$89.3672	$89.37	$89.35	$89.40
Purchase #7	$31.88	3.544%	$33.0098	$33.01	$33.00	$33.00
7 purchase totals =	$939.88		$1,040.6531	$1,040.66	$1,040.60	$1,040.70