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	$57.29	7.321%	$61.4842	$61.48	$61.50	$61.50
Purchase #2	$112.57	12.215%	$126.3204	$126.32	$126.30	$126.30
Purchase #3	$84.73	5.193%	$89.13	$89.13	$89.15	$89.10
Purchase #4	$118.69	11.625%	$132.4877	$132.49	$132.50	$132.50
Purchase #5	$9.79	10.155%	$10.7842	$10.78	$10.80	$10.80
Purchase #6	$128.73	10.802%	$142.6354	$142.64	$142.65	$142.60
Purchase #7	$173.78	12.212%	$195.002	$195.00	$195.00	$195.00
7 purchase totals =	$685.58		$757.8439	$757.84	$757.90	$757.80