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	$207.32	4.292%	$216.2182	$216.22	$216.20	$216.20
Purchase #2	$197.93	13.270%	$224.1953	$224.20	$224.20	$224.20
Purchase #3	$69.93	12.724%	$78.8279	$78.83	$78.85	$78.80
Purchase #4	$108.37	7.808%	$116.8315	$116.83	$116.85	$116.80
Purchase #5	$58.76	7.384%	$63.0988	$63.10	$63.10	$63.10
Purchase #6	$85.66	6.140%	$90.9195	$90.92	$90.90	$90.90
Purchase #7	$212.81	9.863%	$233.7995	$233.80	$233.80	$233.80
7 purchase totals =	$940.78		$1,023.8907	$1,023.90	$1,023.90	$1,023.80