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	$85.27	9.215%	$93.1276	$93.13	$93.15	$93.10
Purchase #2	$248.52	5.210%	$261.4679	$261.47	$261.45	$261.50
Purchase #3	$177.57	4.322%	$185.2446	$185.24	$185.25	$185.20
Purchase #4	$118.83	5.191%	$124.9985	$125.00	$125.00	$125.00
Purchase #5	$216.27	5.259%	$227.6436	$227.64	$227.65	$227.60
Purchase #6	$19.93	9.483%	$21.82	$21.82	$21.80	$21.80
Purchase #7	$79.57	12.538%	$89.5465	$89.55	$89.55	$89.50
7 purchase totals =	$945.96		$1,003.8487	$1,003.85	$1,003.85	$1,003.70