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	$128.75	10.651%	$142.4632	$142.46	$142.45	$142.50
Purchase #2	$233.89	13.355%	$265.126	$265.13	$265.15	$265.10
Purchase #3	$238.61	12.681%	$268.8681	$268.87	$268.85	$268.90
Purchase #4	$228.36	7.642%	$245.8113	$245.81	$245.80	$245.80
Purchase #5	$51.30	10.533%	$56.7034	$56.70	$56.70	$56.70
Purchase #6	$38.50	11.504%	$42.929	$42.93	$42.95	$42.90
Purchase #7	$246.46	3.682%	$255.5347	$255.53	$255.55	$255.50
7 purchase totals =	$1,165.87		$1,277.4357	$1,277.43	$1,277.45	$1,277.40