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	$182.82	7.540%	$196.6046	$196.60	$196.60	$196.60
Purchase #2	$87.91	3.314%	$90.8233	$90.82	$90.80	$90.80
Purchase #3	$222.86	8.655%	$242.1485	$242.15	$242.15	$242.10
Purchase #4	$120.47	8.738%	$130.9967	$131.00	$131.00	$131.00
Purchase #5	$28.93	8.155%	$31.2892	$31.29	$31.30	$31.30
Purchase #6	$117.68	9.455%	$128.8066	$128.81	$128.80	$128.80
Purchase #7	$76.73	9.215%	$83.8007	$83.80	$83.80	$83.80
7 purchase totals =	$837.40		$904.4696	$904.47	$904.45	$904.40