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	$205.61	3.261%	$212.3149	$212.31	$212.30	$212.30
Purchase #2	$52.67	12.641%	$59.328	$59.33	$59.35	$59.30
Purchase #3	$119.41	9.366%	$130.5939	$130.59	$130.60	$130.60
Purchase #4	$95.78	5.365%	$100.9186	$100.92	$100.90	$100.90
Purchase #5	$202.51	11.285%	$225.3633	$225.36	$225.35	$225.40
Purchase #6	$171.83	9.292%	$187.7964	$187.80	$187.80	$187.80
Purchase #7	$90.26	11.366%	$100.519	$100.52	$100.50	$100.50
7 purchase totals =	$938.07		$1,016.8341	$1,016.83	$1,016.80	$1,016.80