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	$114.87	4.264%	$119.7681	$119.77	$119.75	$119.80
Purchase #2	$214.42	3.662%	$222.2721	$222.27	$222.25	$222.30
Purchase #3	$108.29	6.688%	$115.5324	$115.53	$115.55	$115.50
Purchase #4	$23.44	12.291%	$26.321	$26.32	$26.30	$26.30
Purchase #5	$53.85	10.623%	$59.5705	$59.57	$59.55	$59.60
Purchase #6	$185.95	11.107%	$206.6035	$206.60	$206.60	$206.60
Purchase #7	$105.57	10.332%	$116.4775	$116.48	$116.50	$116.50
7 purchase totals =	$806.39		$866.5451	$866.54	$866.50	$866.60