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	$181.58	6.801%	$193.9293	$193.93	$193.95	$193.90
Purchase #2	$164.29	11.257%	$182.7841	$182.78	$182.80	$182.80
Purchase #3	$75.25	13.799%	$85.6337	$85.63	$85.65	$85.60
Purchase #4	$56.65	10.364%	$62.5212	$62.52	$62.50	$62.50
Purchase #5	$38.45	8.271%	$41.6302	$41.63	$41.65	$41.60
Purchase #6	$187.29	11.837%	$209.4595	$209.46	$209.45	$209.50
Purchase #7	$123.94	5.383%	$130.6117	$130.61	$130.60	$130.60
7 purchase totals =	$827.45		$906.5697	$906.56	$906.60	$906.50