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	$250.38	5.173%	$263.3322	$263.33	$263.35	$263.30
Purchase #2	$114.69	5.314%	$120.7846	$120.78	$120.80	$120.80
Purchase #3	$33.56	6.124%	$35.6152	$35.62	$35.60	$35.60
Purchase #4	$42.60	12.423%	$47.8922	$47.89	$47.90	$47.90
Purchase #5	$185.38	8.174%	$200.533	$200.53	$200.55	$200.50
Purchase #6	$206.55	4.242%	$215.3119	$215.31	$215.30	$215.30
Purchase #7	$164.45	10.680%	$182.0133	$182.01	$182.00	$182.00
7 purchase totals =	$997.61		$1,065.4824	$1,065.47	$1,065.50	$1,065.40