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	$129.28	3.427%	$133.7104	$133.71	$133.70	$133.70
Purchase #2	$94.83	4.404%	$99.0063	$99.01	$99.00	$99.00
Purchase #3	$112.40	12.860%	$126.8546	$126.85	$126.85	$126.90
Purchase #4	$126.91	11.822%	$141.9133	$141.91	$141.90	$141.90
Purchase #5	$171.54	4.157%	$178.6709	$178.67	$178.65	$178.70
Purchase #6	$98.34	7.659%	$105.8719	$105.87	$105.85	$105.90
Purchase #7	$159.76	11.116%	$177.5189	$177.52	$177.50	$177.50
7 purchase totals =	$893.06		$963.5463	$963.54	$963.45	$963.60