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	$82.55	8.817%	$89.8284	$89.83	$89.85	$89.80
Purchase #2	$39.89	11.751%	$44.5775	$44.58	$44.60	$44.60
Purchase #3	$93.53	6.547%	$99.6534	$99.65	$99.65	$99.70
Purchase #4	$156.81	3.422%	$162.176	$162.18	$162.20	$162.20
Purchase #5	$136.59	12.533%	$153.7088	$153.71	$153.70	$153.70
Purchase #6	$250.53	12.860%	$282.7482	$282.75	$282.75	$282.70
Purchase #7	$166.76	7.218%	$178.7967	$178.80	$178.80	$178.80
7 purchase totals =	$926.66		$1,011.4890	$1,011.50	$1,011.55	$1,011.50