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	$225.76	13.174%	$255.5016	$255.50	$255.50	$255.50
Purchase #2	$142.84	9.552%	$156.4841	$156.48	$156.50	$156.50
Purchase #3	$210.48	3.839%	$218.5603	$218.56	$218.55	$218.60
Purchase #4	$84.83	4.840%	$88.9358	$88.94	$88.95	$88.90
Purchase #5	$88.30	7.383%	$94.8192	$94.82	$94.80	$94.80
Purchase #6	$163.31	5.536%	$172.3508	$172.35	$172.35	$172.40
Purchase #7	$102.29	5.610%	$108.0285	$108.03	$108.05	$108.00
7 purchase totals =	$1,017.81		$1,094.6803	$1,094.68	$1,094.70	$1,094.70