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	$127.96	5.802%	$135.3842	$135.38	$135.40	$135.40
Purchase #2	$248.64	5.359%	$261.9646	$261.96	$261.95	$262.00
Purchase #3	$225.61	5.496%	$238.0095	$238.01	$238.00	$238.00
Purchase #4	$80.27	7.149%	$86.0085	$86.01	$86.00	$86.00
Purchase #5	$118.82	4.787%	$124.5079	$124.51	$124.50	$124.50
Purchase #6	$63.65	13.583%	$72.2956	$72.30	$72.30	$72.30
Purchase #7	$56.96	5.286%	$59.9709	$59.97	$59.95	$60.00
7 purchase totals =	$921.91		$978.1412	$978.14	$978.10	$978.20