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	$5.63	7.594%	$6.0575	$6.06	$6.05	$6.10
Purchase #2	$38.64	11.352%	$43.0264	$43.03	$43.05	$43.00
Purchase #3	$18.54	12.338%	$20.8275	$20.83	$20.85	$20.80
Purchase #4	$208.58	7.359%	$223.9294	$223.93	$223.95	$223.90
Purchase #5	$171.51	8.223%	$185.6133	$185.61	$185.60	$185.60
Purchase #6	$178.82	5.758%	$189.1165	$189.12	$189.10	$189.10
Purchase #7	$61.82	3.365%	$63.9002	$63.90	$63.90	$63.90
7 purchase totals =	$683.54		$732.4708	$732.48	$732.50	$732.40