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	$233.89	13.385%	$265.1962	$265.20	$265.20	$265.20
Purchase #2	$241.82	3.755%	$250.9003	$250.90	$250.90	$250.90
Purchase #3	$72.90	7.102%	$78.0774	$78.08	$78.10	$78.10
Purchase #4	$142.98	12.863%	$161.3715	$161.37	$161.35	$161.40
Purchase #5	$197.40	13.390%	$223.8319	$223.83	$223.85	$223.80
Purchase #6	$92.30	3.344%	$95.3865	$95.39	$95.40	$95.40
Purchase #7	$8.71	6.792%	$9.3016	$9.30	$9.30	$9.30
7 purchase totals =	$990.00		$1,084.0654	$1,084.07	$1,084.10	$1,084.10