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	$190.42	3.829%	$197.7112	$197.71	$197.70	$197.70
Purchase #2	$112.47	9.376%	$123.0152	$123.02	$123.00	$123.00
Purchase #3	$82.25	10.524%	$90.906	$90.91	$90.90	$90.90
Purchase #4	$143.46	9.661%	$157.3197	$157.32	$157.30	$157.30
Purchase #5	$163.68	10.261%	$180.4752	$180.48	$180.50	$180.50
Purchase #6	$37.68	8.602%	$40.9212	$40.92	$40.90	$40.90
Purchase #7	$13.77	4.799%	$14.4308	$14.43	$14.45	$14.40
7 purchase totals =	$743.73		$804.7793	$804.79	$804.75	$804.70