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	$213.60	6.655%	$227.8151	$227.82	$227.80	$227.80
Purchase #2	$28.69	8.557%	$31.145	$31.15	$31.15	$31.10
Purchase #3	$78.85	9.305%	$86.187	$86.19	$86.20	$86.20
Purchase #4	$104.84	4.449%	$109.5043	$109.50	$109.50	$109.50
Purchase #5	$244.62	12.256%	$274.6006	$274.60	$274.60	$274.60
Purchase #6	$205.53	8.230%	$222.4451	$222.45	$222.45	$222.40
Purchase #7	$82.36	6.371%	$87.6072	$87.61	$87.60	$87.60
7 purchase totals =	$958.49		$1,039.3043	$1,039.32	$1,039.30	$1,039.20