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	$172.60	10.287%	$190.3554	$190.36	$190.35	$190.40
Purchase #2	$137.83	11.705%	$153.963	$153.96	$153.95	$154.00
Purchase #3	$78.90	5.765%	$83.4486	$83.45	$83.45	$83.40
Purchase #4	$156.90	5.365%	$165.3177	$165.32	$165.30	$165.30
Purchase #5	$222.37	6.378%	$236.5528	$236.55	$236.55	$236.60
Purchase #6	$92.61	3.831%	$96.1579	$96.16	$96.15	$96.20
Purchase #7	$109.78	8.600%	$119.2211	$119.22	$119.20	$119.20
7 purchase totals =	$970.99		$1,045.0165	$1,045.02	$1,044.95	$1,045.10