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	$98.42	7.262%	$105.5673	$105.57	$105.55	$105.60
Purchase #2	$21.28	5.357%	$22.42	$22.42	$22.40	$22.40
Purchase #3	$126.41	13.404%	$143.354	$143.35	$143.35	$143.40
Purchase #4	$85.89	9.720%	$94.2385	$94.24	$94.25	$94.20
Purchase #5	$222.71	9.152%	$243.0924	$243.09	$243.10	$243.10
Purchase #6	$129.34	8.725%	$140.6249	$140.62	$140.60	$140.60
Purchase #7	$184.82	7.297%	$198.3063	$198.31	$198.30	$198.30
7 purchase totals =	$868.87		$947.6034	$947.60	$947.55	$947.60