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	$134.39	4.806%	$140.8488	$140.85	$140.85	$140.80
Purchase #2	$245.40	6.523%	$261.4074	$261.41	$261.40	$261.40
Purchase #3	$164.72	6.723%	$175.7941	$175.79	$175.80	$175.80
Purchase #4	$156.71	10.236%	$172.7508	$172.75	$172.75	$172.80
Purchase #5	$122.62	7.572%	$131.9048	$131.90	$131.90	$131.90
Purchase #6	$246.89	7.673%	$265.8339	$265.83	$265.85	$265.80
Purchase #7	$164.60	8.147%	$178.01	$178.01	$178.00	$178.00
7 purchase totals =	$1,235.33		$1,326.5498	$1,326.54	$1,326.55	$1,326.50