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	$32.87	9.224%	$35.9019	$35.90	$35.90	$35.90
Purchase #2	$103.78	9.523%	$113.663	$113.66	$113.65	$113.70
Purchase #3	$60.42	3.789%	$62.7093	$62.71	$62.70	$62.70
Purchase #4	$42.84	9.442%	$46.885	$46.89	$46.90	$46.90
Purchase #5	$81.50	4.664%	$85.3012	$85.30	$85.30	$85.30
Purchase #6	$169.47	6.786%	$180.9702	$180.97	$180.95	$181.00
Purchase #7	$196.53	11.313%	$218.7634	$218.76	$218.75	$218.80
7 purchase totals =	$687.41		$744.1940	$744.19	$744.15	$744.30