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	$43.79	6.275%	$46.5378	$46.54	$46.55	$46.50
Purchase #2	$242.51	3.706%	$251.4974	$251.50	$251.50	$251.50
Purchase #3	$173.32	13.293%	$196.3594	$196.36	$196.35	$196.40
Purchase #4	$239.98	7.700%	$258.4585	$258.46	$258.45	$258.50
Purchase #5	$12.45	11.846%	$13.9248	$13.92	$13.90	$13.90
Purchase #6	$94.45	7.322%	$101.3656	$101.37	$101.35	$101.40
Purchase #7	$95.93	9.688%	$105.2237	$105.22	$105.20	$105.20
7 purchase totals =	$902.43		$973.3672	$973.37	$973.30	$973.40