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	$35.87	13.473%	$40.7028	$40.70	$40.70	$40.70
Purchase #2	$216.65	9.632%	$237.5177	$237.52	$237.50	$237.50
Purchase #3	$89.81	11.782%	$100.3914	$100.39	$100.40	$100.40
Purchase #4	$81.86	5.749%	$86.5661	$86.57	$86.55	$86.60
Purchase #5	$113.72	6.162%	$120.7274	$120.73	$120.75	$120.70
Purchase #6	$228.72	6.581%	$243.7721	$243.77	$243.75	$243.80
Purchase #7	$18.29	8.534%	$19.8509	$19.85	$19.85	$19.90
7 purchase totals =	$784.92		$849.5284	$849.53	$849.50	$849.60