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	$84.30	13.130%	$95.3686	$95.37	$95.35	$95.40
Purchase #2	$148.88	4.760%	$155.9667	$155.97	$155.95	$156.00
Purchase #3	$78.63	11.247%	$87.4735	$87.47	$87.45	$87.50
Purchase #4	$216.88	9.220%	$236.8763	$236.88	$236.90	$236.90
Purchase #5	$143.90	5.501%	$151.8159	$151.82	$151.80	$151.80
Purchase #6	$86.82	12.706%	$97.8513	$97.85	$97.85	$97.90
Purchase #7	$141.90	9.627%	$155.5607	$155.56	$155.55	$155.60
7 purchase totals =	$901.31		$980.9130	$980.92	$980.85	$981.10