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	$52.63	7.671%	$56.6672	$56.67	$56.65	$56.70
Purchase #2	$90.97	11.589%	$101.5125	$101.51	$101.50	$101.50
Purchase #3	$106.37	7.814%	$114.6818	$114.68	$114.70	$114.70
Purchase #4	$59.67	8.770%	$64.9031	$64.90	$64.90	$64.90
Purchase #5	$54.43	4.524%	$56.8924	$56.89	$56.90	$56.90
Purchase #6	$141.88	10.201%	$156.3532	$156.35	$156.35	$156.40
Purchase #7	$215.90	5.829%	$228.4848	$228.48	$228.50	$228.50
7 purchase totals =	$721.85		$779.4950	$779.48	$779.50	$779.60