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	$156.46	9.355%	$171.0968	$171.10	$171.10	$171.10
Purchase #2	$103.45	11.216%	$115.053	$115.05	$115.05	$115.10
Purchase #3	$247.33	3.651%	$256.36	$256.36	$256.35	$256.40
Purchase #4	$33.62	3.622%	$34.8377	$34.84	$34.85	$34.80
Purchase #5	$139.96	6.246%	$148.7019	$148.70	$148.70	$148.70
Purchase #6	$136.88	13.667%	$155.5874	$155.59	$155.60	$155.60
Purchase #7	$213.69	13.328%	$242.1706	$242.17	$242.15	$242.20
7 purchase totals =	$1,031.39		$1,123.8074	$1,123.81	$1,123.80	$1,123.90