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	$185.81	11.464%	$207.1113	$207.11	$207.10	$207.10
Purchase #2	$125.72	11.268%	$139.8861	$139.89	$139.90	$139.90
Purchase #3	$233.35	9.411%	$255.3106	$255.31	$255.30	$255.30
Purchase #4	$38.48	3.340%	$39.7652	$39.77	$39.75	$39.80
Purchase #5	$101.88	8.680%	$110.7232	$110.72	$110.70	$110.70
Purchase #6	$91.83	10.360%	$101.3436	$101.34	$101.35	$101.30
Purchase #7	$230.46	11.858%	$257.7879	$257.79	$257.80	$257.80
7 purchase totals =	$1,007.53		$1,111.9279	$1,111.93	$1,111.90	$1,111.90