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	$38.68	6.731%	$41.2836	$41.28	$41.30	$41.30
Purchase #2	$161.64	4.572%	$169.0302	$169.03	$169.05	$169.00
Purchase #3	$63.64	13.126%	$71.9934	$71.99	$72.00	$72.00
Purchase #4	$132.59	11.418%	$147.7291	$147.73	$147.75	$147.70
Purchase #5	$146.59	12.277%	$164.5869	$164.59	$164.60	$164.60
Purchase #6	$89.81	11.436%	$100.0807	$100.08	$100.10	$100.10
Purchase #7	$68.85	5.497%	$72.6347	$72.63	$72.65	$72.60
7 purchase totals =	$701.80		$767.3386	$767.33	$767.45	$767.30