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	$191.98	12.249%	$215.4956	$215.50	$215.50	$215.50
Purchase #2	$64.83	11.502%	$72.2867	$72.29	$72.30	$72.30
Purchase #3	$130.28	5.573%	$137.5405	$137.54	$137.55	$137.50
Purchase #4	$205.89	4.642%	$215.4474	$215.45	$215.45	$215.40
Purchase #5	$10.48	8.438%	$11.3643	$11.36	$11.35	$11.40
Purchase #6	$82.78	3.565%	$85.7311	$85.73	$85.75	$85.70
Purchase #7	$197.55	4.256%	$205.9577	$205.96	$205.95	$206.00
7 purchase totals =	$883.79		$943.8233	$943.83	$943.85	$943.80