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	$42.75	13.179%	$48.384	$48.38	$48.40	$48.40
Purchase #2	$63.47	8.683%	$68.9811	$68.98	$69.00	$69.00
Purchase #3	$64.78	12.705%	$73.0103	$73.01	$73.00	$73.00
Purchase #4	$28.27	11.728%	$31.5855	$31.59	$31.60	$31.60
Purchase #5	$194.70	9.784%	$213.7494	$213.75	$213.75	$213.70
Purchase #6	$27.82	11.490%	$31.0165	$31.02	$31.00	$31.00
Purchase #7	$211.53	4.869%	$221.8294	$221.83	$221.85	$221.80
7 purchase totals =	$633.32		$688.5562	$688.56	$688.60	$688.50