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	$204.86	11.598%	$228.6197	$228.62	$228.60	$228.60
Purchase #2	$202.28	4.238%	$210.8526	$210.85	$210.85	$210.90
Purchase #3	$79.48	4.588%	$83.1265	$83.13	$83.15	$83.10
Purchase #4	$190.51	9.611%	$208.8199	$208.82	$208.80	$208.80
Purchase #5	$160.77	9.381%	$175.8518	$175.85	$175.85	$175.90
Purchase #6	$29.54	7.595%	$31.7836	$31.78	$31.80	$31.80
Purchase #7	$59.56	10.729%	$65.9502	$65.95	$65.95	$66.00
7 purchase totals =	$927.00		$1,005.0043	$1,005.00	$1,005.00	$1,005.10