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	$215.85	4.248%	$225.0193	$225.02	$225.00	$225.00
Purchase #2	$58.59	4.169%	$61.0326	$61.03	$61.05	$61.00
Purchase #3	$111.92	7.143%	$119.9144	$119.91	$119.90	$119.90
Purchase #4	$151.91	11.136%	$168.8267	$168.83	$168.85	$168.80
Purchase #5	$165.54	8.664%	$179.8824	$179.88	$179.90	$179.90
Purchase #6	$56.55	3.535%	$58.549	$58.55	$58.55	$58.50
Purchase #7	$150.77	13.843%	$171.6411	$171.64	$171.65	$171.60
7 purchase totals =	$911.13		$984.8655	$984.86	$984.90	$984.70