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	$218.42	10.712%	$241.8172	$241.82	$241.80	$241.80
Purchase #2	$212.26	5.505%	$223.9449	$223.94	$223.95	$223.90
Purchase #3	$126.30	8.863%	$137.494	$137.49	$137.50	$137.50
Purchase #4	$120.26	8.196%	$130.1165	$130.12	$130.10	$130.10
Purchase #5	$201.62	6.856%	$215.4431	$215.44	$215.45	$215.40
Purchase #6	$17.86	5.624%	$18.8644	$18.86	$18.85	$18.90
Purchase #7	$86.86	12.259%	$97.5082	$97.51	$97.50	$97.50
7 purchase totals =	$983.58		$1,065.1883	$1,065.18	$1,065.15	$1,065.10