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	$184.43	13.686%	$209.6711	$209.67	$209.65	$209.70
Purchase #2	$196.27	9.795%	$215.4946	$215.49	$215.50	$215.50
Purchase #3	$24.95	10.232%	$27.5029	$27.50	$27.50	$27.50
Purchase #4	$85.76	4.212%	$89.3722	$89.37	$89.35	$89.40
Purchase #5	$136.41	5.210%	$143.517	$143.52	$143.50	$143.50
Purchase #6	$96.34	3.102%	$99.3285	$99.33	$99.35	$99.30
Purchase #7	$203.67	13.659%	$231.4893	$231.49	$231.50	$231.50
7 purchase totals =	$927.83		$1,016.3756	$1,016.37	$1,016.35	$1,016.40