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	$166.55	8.681%	$181.0082	$181.01	$181.00	$181.00
Purchase #2	$36.99	7.272%	$39.6799	$39.68	$39.70	$39.70
Purchase #3	$142.29	10.768%	$157.6118	$157.61	$157.60	$157.60
Purchase #4	$226.54	10.737%	$250.8636	$250.86	$250.85	$250.90
Purchase #5	$78.51	13.140%	$88.8262	$88.83	$88.85	$88.80
Purchase #6	$210.53	10.157%	$231.9135	$231.91	$231.90	$231.90
Purchase #7	$220.37	11.868%	$246.5235	$246.52	$246.50	$246.50
7 purchase totals =	$1,081.78		$1,196.4267	$1,196.42	$1,196.40	$1,196.40