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	$223.91	7.577%	$240.8757	$240.88	$240.90	$240.90
Purchase #2	$73.94	5.813%	$78.2381	$78.24	$78.25	$78.20
Purchase #3	$244.46	5.127%	$256.9935	$256.99	$257.00	$257.00
Purchase #4	$242.71	10.151%	$267.3475	$267.35	$267.35	$267.30
Purchase #5	$126.47	4.633%	$132.3294	$132.33	$132.35	$132.30
Purchase #6	$111.34	3.185%	$114.8862	$114.89	$114.90	$114.90
Purchase #7	$95.81	5.290%	$100.8783	$100.88	$100.90	$100.90
7 purchase totals =	$1,118.64		$1,191.5487	$1,191.56	$1,191.65	$1,191.50