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	$22.32	12.137%	$25.029	$25.03	$25.05	$25.00
Purchase #2	$178.34	12.625%	$200.8554	$200.86	$200.85	$200.90
Purchase #3	$105.56	6.207%	$112.1121	$112.11	$112.10	$112.10
Purchase #4	$37.28	6.776%	$39.8061	$39.81	$39.80	$39.80
Purchase #5	$191.74	10.735%	$212.3233	$212.32	$212.30	$212.30
Purchase #6	$30.53	3.440%	$31.5802	$31.58	$31.60	$31.60
Purchase #7	$16.79	11.788%	$18.7692	$18.77	$18.75	$18.80
7 purchase totals =	$582.56		$640.4753	$640.48	$640.45	$640.50