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	$209.74	7.542%	$225.5586	$225.56	$225.55	$225.60
Purchase #2	$35.32	12.523%	$39.7431	$39.74	$39.75	$39.70
Purchase #3	$46.89	10.646%	$51.8819	$51.88	$51.90	$51.90
Purchase #4	$207.49	5.509%	$218.9206	$218.92	$218.90	$218.90
Purchase #5	$161.72	4.319%	$168.7047	$168.70	$168.70	$168.70
Purchase #6	$67.73	6.874%	$72.3858	$72.39	$72.40	$72.40
Purchase #7	$32.65	11.397%	$36.3711	$36.37	$36.35	$36.40
7 purchase totals =	$761.54		$813.5658	$813.56	$813.55	$813.60