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	$206.29	3.171%	$212.8315	$212.83	$212.85	$212.80
Purchase #2	$162.44	7.365%	$174.4037	$174.40	$174.40	$174.40
Purchase #3	$179.66	6.622%	$191.5571	$191.56	$191.55	$191.60
Purchase #4	$208.38	13.526%	$236.5655	$236.57	$236.55	$236.60
Purchase #5	$57.66	3.274%	$59.5478	$59.55	$59.55	$59.50
Purchase #6	$234.72	8.185%	$253.9318	$253.93	$253.95	$253.90
Purchase #7	$35.84	13.193%	$40.5684	$40.57	$40.55	$40.60
7 purchase totals =	$1,084.99		$1,169.4058	$1,169.41	$1,169.40	$1,169.40