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	$141.76	7.773%	$152.779	$152.78	$152.80	$152.80
Purchase #2	$196.86	10.487%	$217.5047	$217.50	$217.50	$217.50
Purchase #3	$195.43	7.746%	$210.568	$210.57	$210.55	$210.60
Purchase #4	$100.31	11.404%	$111.7494	$111.75	$111.75	$111.70
Purchase #5	$87.86	6.331%	$93.4224	$93.42	$93.40	$93.40
Purchase #6	$102.41	4.257%	$106.7696	$106.77	$106.75	$106.80
Purchase #7	$119.67	3.270%	$123.5832	$123.58	$123.60	$123.60
7 purchase totals =	$944.30		$1,016.3763	$1,016.37	$1,016.35	$1,016.40