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	$117.45	11.815%	$131.3267	$131.33	$131.35	$131.30
Purchase #2	$112.56	7.546%	$121.0538	$121.05	$121.05	$121.10
Purchase #3	$115.45	7.352%	$123.9379	$123.94	$123.95	$123.90
Purchase #4	$210.47	5.659%	$222.3805	$222.38	$222.40	$222.40
Purchase #5	$36.46	3.245%	$37.6431	$37.64	$37.65	$37.60
Purchase #6	$150.44	12.835%	$169.749	$169.75	$169.75	$169.70
Purchase #7	$81.43	10.120%	$89.6707	$89.67	$89.65	$89.70
7 purchase totals =	$824.26		$895.7617	$895.76	$895.80	$895.70