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	$213.60	9.854%	$234.6481	$234.65	$234.65	$234.60
Purchase #2	$100.82	4.679%	$105.5374	$105.54	$105.55	$105.50
Purchase #3	$110.98	12.538%	$124.8947	$124.89	$124.90	$124.90
Purchase #4	$236.87	3.410%	$244.9473	$244.95	$244.95	$244.90
Purchase #5	$163.71	3.635%	$169.6609	$169.66	$169.65	$169.70
Purchase #6	$140.41	10.312%	$154.8891	$154.89	$154.90	$154.90
Purchase #7	$46.30	10.843%	$51.3203	$51.32	$51.30	$51.30
7 purchase totals =	$1,012.69		$1,085.8978	$1,085.90	$1,085.90	$1,085.80