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	$229.82	4.131%	$239.3139	$239.31	$239.30	$239.30
Purchase #2	$232.68	12.558%	$261.9	$261.90	$261.90	$261.90
Purchase #3	$59.96	10.510%	$66.2618	$66.26	$66.25	$66.30
Purchase #4	$88.83	12.510%	$99.9426	$99.94	$99.95	$99.90
Purchase #5	$134.47	13.656%	$152.8332	$152.83	$152.85	$152.80
Purchase #6	$36.72	7.505%	$39.4758	$39.48	$39.50	$39.50
Purchase #7	$212.76	6.284%	$226.1298	$226.13	$226.15	$226.10
7 purchase totals =	$995.24		$1,085.8571	$1,085.85	$1,085.90	$1,085.80