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	$232.72	10.660%	$257.528	$257.53	$257.55	$257.50
Purchase #2	$40.76	10.781%	$45.1543	$45.15	$45.15	$45.20
Purchase #3	$171.48	10.822%	$190.0376	$190.04	$190.05	$190.00
Purchase #4	$19.90	9.712%	$21.8327	$21.83	$21.85	$21.80
Purchase #5	$243.72	9.506%	$266.888	$266.89	$266.90	$266.90
Purchase #6	$118.94	10.666%	$131.6261	$131.63	$131.65	$131.60
Purchase #7	$115.92	4.802%	$121.4865	$121.49	$121.50	$121.50
7 purchase totals =	$943.44		$1,034.5532	$1,034.56	$1,034.65	$1,034.50