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	$162.54	3.683%	$168.5263	$168.53	$168.55	$168.50
Purchase #2	$43.78	5.119%	$46.0211	$46.02	$46.00	$46.00
Purchase #3	$147.31	13.219%	$166.7829	$166.78	$166.80	$166.80
Purchase #4	$119.27	4.677%	$124.8483	$124.85	$124.85	$124.80
Purchase #5	$81.57	3.509%	$84.4323	$84.43	$84.45	$84.40
Purchase #6	$63.82	11.797%	$71.3488	$71.35	$71.35	$71.30
Purchase #7	$242.27	7.439%	$260.2925	$260.29	$260.30	$260.30
7 purchase totals =	$860.56		$922.2522	$922.25	$922.30	$922.10