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	$191.80	7.117%	$205.4504	$205.45	$205.45	$205.50
Purchase #2	$217.54	5.322%	$229.1175	$229.12	$229.10	$229.10
Purchase #3	$248.58	10.233%	$274.0172	$274.02	$274.00	$274.00
Purchase #4	$179.91	6.660%	$191.892	$191.89	$191.90	$191.90
Purchase #5	$13.48	6.418%	$14.3451	$14.35	$14.35	$14.30
Purchase #6	$36.76	5.789%	$38.888	$38.89	$38.90	$38.90
Purchase #7	$150.42	13.762%	$171.1208	$171.12	$171.10	$171.10
7 purchase totals =	$1,038.49		$1,124.8310	$1,124.84	$1,124.80	$1,124.80