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	$223.59	8.691%	$243.0222	$243.02	$243.00	$243.00
Purchase #2	$239.98	9.832%	$263.5748	$263.57	$263.55	$263.60
Purchase #3	$104.64	6.266%	$111.1967	$111.20	$111.20	$111.20
Purchase #4	$77.76	11.298%	$86.5453	$86.55	$86.55	$86.50
Purchase #5	$9.27	7.689%	$9.9828	$9.98	$10.00	$10.00
Purchase #6	$208.78	11.828%	$233.4745	$233.47	$233.45	$233.50
Purchase #7	$56.39	9.629%	$61.8198	$61.82	$61.80	$61.80
7 purchase totals =	$920.41		$1,009.6161	$1,009.61	$1,009.55	$1,009.60