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	$182.65	6.205%	$193.9834	$193.98	$194.00	$194.00
Purchase #2	$164.50	9.850%	$180.7033	$180.70	$180.70	$180.70
Purchase #3	$38.38	11.850%	$42.928	$42.93	$42.95	$42.90
Purchase #4	$90.63	11.126%	$100.7135	$100.71	$100.70	$100.70
Purchase #5	$185.80	5.484%	$195.9893	$195.99	$196.00	$196.00
Purchase #6	$192.57	11.852%	$215.3934	$215.39	$215.40	$215.40
Purchase #7	$77.33	12.513%	$87.0063	$87.01	$87.00	$87.00
7 purchase totals =	$931.86		$1,016.7172	$1,016.71	$1,016.75	$1,016.70