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	$114.73	8.657%	$124.6622	$124.66	$124.65	$124.70
Purchase #2	$168.32	11.571%	$187.7963	$187.80	$187.80	$187.80
Purchase #3	$190.80	11.227%	$212.2211	$212.22	$212.20	$212.20
Purchase #4	$128.95	6.362%	$137.1538	$137.15	$137.15	$137.20
Purchase #5	$80.67	11.350%	$89.826	$89.83	$89.85	$89.80
Purchase #6	$76.89	8.555%	$83.4679	$83.47	$83.45	$83.50
Purchase #7	$40.31	7.343%	$43.27	$43.27	$43.25	$43.30
7 purchase totals =	$800.67		$878.3973	$878.40	$878.35	$878.50