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	$192.83	8.665%	$209.5387	$209.54	$209.55	$209.50
Purchase #2	$165.45	8.471%	$179.4653	$179.47	$179.45	$179.50
Purchase #3	$186.35	4.562%	$194.8513	$194.85	$194.85	$194.90
Purchase #4	$121.75	3.672%	$126.2207	$126.22	$126.20	$126.20
Purchase #5	$198.77	3.606%	$205.9376	$205.94	$205.95	$205.90
Purchase #6	$104.69	13.108%	$118.4128	$118.41	$118.40	$118.40
Purchase #7	$86.47	4.570%	$90.4217	$90.42	$90.40	$90.40
7 purchase totals =	$1,056.31		$1,124.8481	$1,124.85	$1,124.80	$1,124.80