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	$52.27	7.226%	$56.047	$56.05	$56.05	$56.00
Purchase #2	$128.29	12.774%	$144.6778	$144.68	$144.70	$144.70
Purchase #3	$202.87	3.210%	$209.3821	$209.38	$209.40	$209.40
Purchase #4	$250.83	13.609%	$284.9655	$284.97	$284.95	$285.00
Purchase #5	$145.67	6.308%	$154.8589	$154.86	$154.85	$154.90
Purchase #6	$85.28	6.278%	$90.6339	$90.63	$90.65	$90.60
Purchase #7	$160.68	8.464%	$174.28	$174.28	$174.30	$174.30
7 purchase totals =	$1,025.89		$1,114.8452	$1,114.85	$1,114.90	$1,114.90