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	$41.92	8.217%	$45.3646	$45.36	$45.35	$45.40
Purchase #2	$215.92	7.324%	$231.734	$231.73	$231.75	$231.70
Purchase #3	$114.52	6.547%	$122.0176	$122.02	$122.00	$122.00
Purchase #4	$240.78	10.147%	$265.2119	$265.21	$265.20	$265.20
Purchase #5	$158.83	13.714%	$180.6119	$180.61	$180.60	$180.60
Purchase #6	$40.28	11.835%	$45.0471	$45.05	$45.05	$45.00
Purchase #7	$183.83	7.129%	$196.9352	$196.94	$196.95	$196.90
7 purchase totals =	$996.08		$1,086.9223	$1,086.92	$1,086.90	$1,086.80