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	$161.26	3.334%	$166.6364	$166.64	$166.65	$166.60
Purchase #2	$178.43	10.339%	$196.8779	$196.88	$196.90	$196.90
Purchase #3	$210.27	3.446%	$217.5159	$217.52	$217.50	$217.50
Purchase #4	$159.41	11.549%	$177.8203	$177.82	$177.80	$177.80
Purchase #5	$150.37	3.293%	$155.3217	$155.32	$155.30	$155.30
Purchase #6	$161.58	3.132%	$166.6407	$166.64	$166.65	$166.60
Purchase #7	$17.70	3.310%	$18.2859	$18.29	$18.30	$18.30
7 purchase totals =	$1,039.02		$1,099.0988	$1,099.11	$1,099.10	$1,099.00