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	$120.83	11.526%	$134.7569	$134.76	$134.75	$134.80
Purchase #2	$119.55	5.154%	$125.7116	$125.71	$125.70	$125.70
Purchase #3	$98.37	13.824%	$111.9687	$111.97	$111.95	$112.00
Purchase #4	$86.50	3.557%	$89.5768	$89.58	$89.60	$89.60
Purchase #5	$100.84	11.791%	$112.73	$112.73	$112.75	$112.70
Purchase #6	$89.57	11.725%	$100.0721	$100.07	$100.05	$100.10
Purchase #7	$28.77	7.617%	$30.9614	$30.96	$30.95	$31.00
7 purchase totals =	$644.43		$705.7775	$705.78	$705.75	$705.90