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	$44.67	10.454%	$49.3398	$49.34	$49.35	$49.30
Purchase #2	$59.72	11.317%	$66.4785	$66.48	$66.50	$66.50
Purchase #3	$201.48	10.291%	$222.2143	$222.21	$222.20	$222.20
Purchase #4	$40.36	13.421%	$45.7767	$45.78	$45.80	$45.80
Purchase #5	$200.56	7.340%	$215.2811	$215.28	$215.30	$215.30
Purchase #6	$223.36	6.571%	$238.037	$238.04	$238.05	$238.00
Purchase #7	$192.41	3.243%	$198.6499	$198.65	$198.65	$198.60
7 purchase totals =	$962.56		$1,035.7773	$1,035.78	$1,035.85	$1,035.70