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	$207.97	6.796%	$222.1036	$222.10	$222.10	$222.10
Purchase #2	$199.76	6.794%	$213.3317	$213.33	$213.35	$213.30
Purchase #3	$80.88	8.326%	$87.6141	$87.61	$87.60	$87.60
Purchase #4	$73.80	3.605%	$76.4605	$76.46	$76.45	$76.50
Purchase #5	$80.63	5.792%	$85.3001	$85.30	$85.30	$85.30
Purchase #6	$250.92	4.202%	$261.4637	$261.46	$261.45	$261.50
Purchase #7	$171.47	5.428%	$180.7774	$180.78	$180.80	$180.80
7 purchase totals =	$1,065.43		$1,127.0511	$1,127.04	$1,127.05	$1,127.10