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	$36.45	13.676%	$41.4349	$41.43	$41.45	$41.40
Purchase #2	$29.96	6.438%	$31.8888	$31.89	$31.90	$31.90
Purchase #3	$214.91	10.668%	$237.8366	$237.84	$237.85	$237.80
Purchase #4	$209.81	11.460%	$233.8542	$233.85	$233.85	$233.90
Purchase #5	$229.54	8.184%	$248.3256	$248.33	$248.35	$248.30
Purchase #6	$139.78	3.129%	$144.1537	$144.15	$144.15	$144.20
Purchase #7	$100.84	4.555%	$105.4333	$105.43	$105.45	$105.40
7 purchase totals =	$961.29		$1,042.9271	$1,042.92	$1,043.00	$1,042.90