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	$84.55	11.791%	$94.5193	$94.52	$94.50	$94.50
Purchase #2	$96.91	8.635%	$105.2782	$105.28	$105.30	$105.30
Purchase #3	$41.48	8.570%	$45.0348	$45.03	$45.05	$45.00
Purchase #4	$62.25	6.663%	$66.3977	$66.40	$66.40	$66.40
Purchase #5	$56.30	6.273%	$59.8317	$59.83	$59.85	$59.80
Purchase #6	$203.53	11.678%	$227.2982	$227.30	$227.30	$227.30
Purchase #7	$72.38	6.614%	$77.1672	$77.17	$77.15	$77.20
7 purchase totals =	$617.40		$675.5271	$675.53	$675.55	$675.50