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	$243.31	10.576%	$269.0425	$269.04	$269.05	$269.00
Purchase #2	$16.73	10.341%	$18.46	$18.46	$18.45	$18.50
Purchase #3	$218.61	3.344%	$225.9203	$225.92	$225.90	$225.90
Purchase #4	$219.72	6.650%	$234.3314	$234.33	$234.35	$234.30
Purchase #5	$208.77	6.768%	$222.8996	$222.90	$222.90	$222.90
Purchase #6	$138.93	4.422%	$145.0735	$145.07	$145.05	$145.10
Purchase #7	$76.64	8.209%	$82.9314	$82.93	$82.95	$82.90
7 purchase totals =	$1,122.71		$1,198.6587	$1,198.65	$1,198.65	$1,198.60