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	$106.56	8.802%	$115.9394	$115.94	$115.95	$115.90
Purchase #2	$63.85	3.692%	$66.2073	$66.21	$66.20	$66.20
Purchase #3	$21.59	5.838%	$22.8504	$22.85	$22.85	$22.90
Purchase #4	$113.86	12.127%	$127.6678	$127.67	$127.65	$127.70
Purchase #5	$82.80	3.452%	$85.6583	$85.66	$85.65	$85.70
Purchase #6	$46.55	6.221%	$49.4459	$49.45	$49.45	$49.40
Purchase #7	$76.43	3.261%	$78.9224	$78.92	$78.90	$78.90
7 purchase totals =	$511.64		$546.6915	$546.70	$546.65	$546.70