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	$54.93	7.499%	$59.0492	$59.05	$59.05	$59.00
Purchase #2	$241.76	8.713%	$262.8245	$262.82	$262.80	$262.80
Purchase #3	$125.67	12.233%	$141.0432	$141.04	$141.05	$141.00
Purchase #4	$223.61	13.529%	$253.8622	$253.86	$253.85	$253.90
Purchase #5	$187.48	13.384%	$212.5723	$212.57	$212.55	$212.60
Purchase #6	$49.75	3.146%	$51.3151	$51.32	$51.30	$51.30
Purchase #7	$27.40	11.477%	$30.5447	$30.54	$30.55	$30.50
7 purchase totals =	$910.60		$1,011.2112	$1,011.20	$1,011.15	$1,011.10