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	$156.69	5.707%	$165.6323	$165.63	$165.65	$165.60
Purchase #2	$131.52	6.841%	$140.5173	$140.52	$140.50	$140.50
Purchase #3	$167.94	11.260%	$186.85	$186.85	$186.85	$186.90
Purchase #4	$47.61	7.210%	$51.0427	$51.04	$51.05	$51.00
Purchase #5	$72.55	3.240%	$74.9006	$74.90	$74.90	$74.90
Purchase #6	$25.85	4.864%	$27.1073	$27.11	$27.10	$27.10
Purchase #7	$44.95	12.334%	$50.4941	$50.49	$50.50	$50.50
7 purchase totals =	$647.11		$696.5443	$696.54	$696.55	$696.50