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	$98.34	5.129%	$103.3839	$103.38	$103.40	$103.40
Purchase #2	$61.53	4.687%	$64.4139	$64.41	$64.40	$64.40
Purchase #3	$66.30	9.712%	$72.7391	$72.74	$72.75	$72.70
Purchase #4	$136.46	4.294%	$142.3196	$142.32	$142.30	$142.30
Purchase #5	$84.90	8.244%	$91.8992	$91.90	$91.90	$91.90
Purchase #6	$161.85	8.635%	$175.8257	$175.83	$175.85	$175.80
Purchase #7	$62.96	3.204%	$64.9772	$64.98	$65.00	$65.00
7 purchase totals =	$672.34		$715.5586	$715.56	$715.60	$715.50