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	$31.66	12.747%	$35.6957	$35.70	$35.70	$35.70
Purchase #2	$234.71	13.129%	$265.5251	$265.53	$265.55	$265.50
Purchase #3	$91.37	13.403%	$103.6163	$103.62	$103.60	$103.60
Purchase #4	$61.55	9.414%	$67.3443	$67.34	$67.35	$67.30
Purchase #5	$184.51	6.667%	$196.8113	$196.81	$196.80	$196.80
Purchase #6	$65.79	13.141%	$74.4355	$74.44	$74.45	$74.40
Purchase #7	$215.66	9.249%	$235.6064	$235.61	$235.60	$235.60
7 purchase totals =	$885.25		$979.0346	$979.05	$979.05	$978.90