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	$33.89	8.723%	$36.8462	$36.85	$36.85	$36.80
Purchase #2	$5.33	5.266%	$5.6107	$5.61	$5.60	$5.60
Purchase #3	$61.93	8.151%	$66.9779	$66.98	$67.00	$67.00
Purchase #4	$138.54	8.352%	$150.1109	$150.11	$150.10	$150.10
Purchase #5	$35.59	10.348%	$39.2729	$39.27	$39.25	$39.30
Purchase #6	$120.70	9.242%	$131.8551	$131.86	$131.85	$131.90
Purchase #7	$168.56	6.339%	$179.245	$179.25	$179.25	$179.20
7 purchase totals =	$564.54		$609.9187	$609.93	$609.90	$609.90