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	$138.48	8.329%	$150.014	$150.01	$150.00	$150.00
Purchase #2	$49.96	11.864%	$55.8873	$55.89	$55.90	$55.90
Purchase #3	$178.34	6.714%	$190.3137	$190.31	$190.30	$190.30
Purchase #4	$147.47	5.717%	$155.9009	$155.90	$155.90	$155.90
Purchase #5	$184.86	7.570%	$198.8539	$198.85	$198.85	$198.90
Purchase #6	$17.96	5.237%	$18.9006	$18.90	$18.90	$18.90
Purchase #7	$222.74	6.752%	$237.7794	$237.78	$237.80	$237.80
7 purchase totals =	$939.81		$1,007.6498	$1,007.64	$1,007.65	$1,007.70