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	$86.98	3.296%	$89.8469	$89.85	$89.85	$89.80
Purchase #2	$87.45	5.416%	$92.1863	$92.19	$92.20	$92.20
Purchase #3	$234.62	7.446%	$252.0898	$252.09	$252.10	$252.10
Purchase #4	$161.27	12.741%	$181.8174	$181.82	$181.80	$181.80
Purchase #5	$61.55	4.732%	$64.4625	$64.46	$64.45	$64.50
Purchase #6	$145.37	4.872%	$152.4524	$152.45	$152.45	$152.50
Purchase #7	$127.79	8.790%	$139.0227	$139.02	$139.00	$139.00
7 purchase totals =	$905.03		$971.8780	$971.88	$971.85	$971.90