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	$111.25	12.291%	$124.9237	$124.92	$124.90	$124.90
Purchase #2	$245.54	4.169%	$255.7766	$255.78	$255.80	$255.80
Purchase #3	$166.60	8.193%	$180.2495	$180.25	$180.25	$180.20
Purchase #4	$68.89	4.417%	$71.9329	$71.93	$71.95	$71.90
Purchase #5	$93.38	9.316%	$102.0793	$102.08	$102.10	$102.10
Purchase #6	$28.43	11.723%	$31.7628	$31.76	$31.75	$31.80
Purchase #7	$179.39	3.872%	$186.336	$186.34	$186.35	$186.30
7 purchase totals =	$893.48		$953.0608	$953.06	$953.10	$953.00