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	$97.74	8.309%	$105.8612	$105.86	$105.85	$105.90
Purchase #2	$163.39	6.806%	$174.5103	$174.51	$174.50	$174.50
Purchase #3	$208.49	5.563%	$220.0883	$220.09	$220.10	$220.10
Purchase #4	$151.78	8.244%	$164.2927	$164.29	$164.30	$164.30
Purchase #5	$43.39	5.332%	$45.7036	$45.70	$45.70	$45.70
Purchase #6	$64.90	4.503%	$67.8224	$67.82	$67.80	$67.80
Purchase #7	$105.86	7.775%	$114.0906	$114.09	$114.10	$114.10
7 purchase totals =	$835.55		$892.3691	$892.36	$892.35	$892.40