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	$143.71	5.600%	$151.7578	$151.76	$151.75	$151.80
Purchase #2	$234.67	13.293%	$265.8647	$265.86	$265.85	$265.90
Purchase #3	$126.72	12.632%	$142.7273	$142.73	$142.75	$142.70
Purchase #4	$185.95	12.683%	$209.534	$209.53	$209.55	$209.50
Purchase #5	$37.66	13.119%	$42.6006	$42.60	$42.60	$42.60
Purchase #6	$89.71	9.380%	$98.1248	$98.12	$98.10	$98.10
Purchase #7	$131.55	9.338%	$143.8341	$143.83	$143.85	$143.80
7 purchase totals =	$949.97		$1,054.4433	$1,054.43	$1,054.45	$1,054.40