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	$157.59	13.398%	$178.7039	$178.70	$178.70	$178.70
Purchase #2	$78.49	10.465%	$86.704	$86.70	$86.70	$86.70
Purchase #3	$8.96	12.855%	$10.1118	$10.11	$10.10	$10.10
Purchase #4	$13.38	8.356%	$14.498	$14.50	$14.50	$14.50
Purchase #5	$167.93	13.357%	$190.3604	$190.36	$190.35	$190.40
Purchase #6	$109.76	8.396%	$118.9754	$118.98	$119.00	$119.00
Purchase #7	$102.41	8.458%	$111.0718	$111.07	$111.05	$111.10
7 purchase totals =	$638.52		$710.4253	$710.42	$710.40	$710.50