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	$39.73	7.141%	$42.5671	$42.57	$42.55	$42.60
Purchase #2	$130.47	5.349%	$137.4488	$137.45	$137.45	$137.40
Purchase #3	$144.76	6.861%	$154.692	$154.69	$154.70	$154.70
Purchase #4	$236.64	7.626%	$254.6862	$254.69	$254.70	$254.70
Purchase #5	$205.90	13.268%	$233.2188	$233.22	$233.20	$233.20
Purchase #6	$27.93	13.423%	$31.679	$31.68	$31.70	$31.70
Purchase #7	$212.72	9.324%	$232.554	$232.55	$232.55	$232.60
7 purchase totals =	$998.15		$1,086.8459	$1,086.85	$1,086.85	$1,086.90