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	$224.79	13.503%	$255.1434	$255.14	$255.15	$255.10
Purchase #2	$132.53	3.245%	$136.8306	$136.83	$136.85	$136.80
Purchase #3	$217.71	13.479%	$247.0551	$247.06	$247.05	$247.10
Purchase #4	$170.85	12.314%	$191.8885	$191.89	$191.90	$191.90
Purchase #5	$196.50	11.481%	$219.0602	$219.06	$219.05	$219.10
Purchase #6	$26.82	10.590%	$29.6602	$29.66	$29.65	$29.70
Purchase #7	$136.34	6.281%	$144.9035	$144.90	$144.90	$144.90
7 purchase totals =	$1,105.54		$1,224.5415	$1,224.54	$1,224.55	$1,224.60