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	$147.68	7.147%	$158.2347	$158.23	$158.25	$158.20
Purchase #2	$135.28	5.723%	$143.0221	$143.02	$143.00	$143.00
Purchase #3	$236.93	8.216%	$256.3962	$256.40	$256.40	$256.40
Purchase #4	$96.42	7.151%	$103.315	$103.32	$103.30	$103.30
Purchase #5	$151.43	13.595%	$172.0169	$172.02	$172.00	$172.00
Purchase #6	$177.56	11.807%	$198.5245	$198.52	$198.50	$198.50
Purchase #7	$55.47	6.427%	$59.0351	$59.04	$59.05	$59.00
7 purchase totals =	$1,000.77		$1,090.5445	$1,090.55	$1,090.50	$1,090.40