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	$62.81	11.311%	$69.9144	$69.91	$69.90	$69.90
Purchase #2	$60.29	6.224%	$64.0424	$64.04	$64.05	$64.00
Purchase #3	$63.75	12.357%	$71.6276	$71.63	$71.65	$71.60
Purchase #4	$176.88	5.735%	$187.0241	$187.02	$187.00	$187.00
Purchase #5	$84.78	5.613%	$89.5387	$89.54	$89.55	$89.50
Purchase #6	$150.38	5.397%	$158.496	$158.50	$158.50	$158.50
Purchase #7	$155.53	10.518%	$171.8886	$171.89	$171.90	$171.90
7 purchase totals =	$754.42		$812.5318	$812.53	$812.55	$812.40