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	$220.56	3.598%	$228.4957	$228.50	$228.50	$228.50
Purchase #2	$236.43	12.125%	$265.0971	$265.10	$265.10	$265.10
Purchase #3	$145.97	7.237%	$156.5338	$156.53	$156.55	$156.50
Purchase #4	$52.45	3.405%	$54.2359	$54.24	$54.25	$54.20
Purchase #5	$104.92	13.362%	$118.9394	$118.94	$118.95	$118.90
Purchase #6	$198.83	11.365%	$221.427	$221.43	$221.45	$221.40
Purchase #7	$45.46	12.377%	$51.0866	$51.09	$51.10	$51.10
7 purchase totals =	$1,004.62		$1,095.8155	$1,095.83	$1,095.90	$1,095.70