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	$215.47	8.254%	$233.2549	$233.25	$233.25	$233.30
Purchase #2	$241.71	6.119%	$256.5002	$256.50	$256.50	$256.50
Purchase #3	$209.66	3.584%	$217.1742	$217.17	$217.15	$217.20
Purchase #4	$202.89	9.508%	$222.1808	$222.18	$222.20	$222.20
Purchase #5	$123.32	10.860%	$136.7126	$136.71	$136.70	$136.70
Purchase #6	$84.86	11.783%	$94.8591	$94.86	$94.85	$94.90
Purchase #7	$144.70	7.498%	$155.5496	$155.55	$155.55	$155.50
7 purchase totals =	$1,222.61		$1,316.2314	$1,316.22	$1,316.20	$1,316.30