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	$38.61	13.117%	$43.6745	$43.67	$43.65	$43.70
Purchase #2	$182.48	4.632%	$190.9325	$190.93	$190.95	$190.90
Purchase #3	$182.77	12.519%	$205.651	$205.65	$205.65	$205.70
Purchase #4	$176.31	13.153%	$199.5001	$199.50	$199.50	$199.50
Purchase #5	$206.57	5.681%	$218.3052	$218.31	$218.30	$218.30
Purchase #6	$188.94	8.280%	$204.5842	$204.58	$204.60	$204.60
Purchase #7	$145.53	13.304%	$164.8913	$164.89	$164.90	$164.90
7 purchase totals =	$1,121.21		$1,227.5388	$1,227.53	$1,227.55	$1,227.60