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	$62.77	10.237%	$69.1958	$69.20	$69.20	$69.20
Purchase #2	$139.90	5.500%	$147.5945	$147.59	$147.60	$147.60
Purchase #3	$85.59	4.688%	$89.6025	$89.60	$89.60	$89.60
Purchase #4	$222.82	12.776%	$251.2875	$251.29	$251.30	$251.30
Purchase #5	$209.50	11.638%	$233.8816	$233.88	$233.90	$233.90
Purchase #6	$78.62	7.291%	$84.3522	$84.35	$84.35	$84.40
Purchase #7	$97.97	11.796%	$109.5265	$109.53	$109.55	$109.50
7 purchase totals =	$897.17		$985.4406	$985.44	$985.50	$985.50