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	$163.93	11.345%	$182.5279	$182.53	$182.55	$182.50
Purchase #2	$231.70	12.813%	$261.3877	$261.39	$261.40	$261.40
Purchase #3	$186.94	12.816%	$210.8982	$210.90	$210.90	$210.90
Purchase #4	$185.61	7.468%	$199.4714	$199.47	$199.45	$199.50
Purchase #5	$49.82	3.605%	$51.616	$51.62	$51.60	$51.60
Purchase #6	$94.89	4.850%	$99.4922	$99.49	$99.50	$99.50
Purchase #7	$240.95	3.551%	$249.5061	$249.51	$249.50	$249.50
7 purchase totals =	$1,153.84		$1,254.8995	$1,254.91	$1,254.90	$1,254.90