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	$90.58	9.129%	$98.849	$98.85	$98.85	$98.80
Purchase #2	$199.75	12.492%	$224.7028	$224.70	$224.70	$224.70
Purchase #3	$46.80	12.863%	$52.8199	$52.82	$52.80	$52.80
Purchase #4	$108.92	7.193%	$116.7546	$116.75	$116.75	$116.80
Purchase #5	$151.57	10.426%	$167.3727	$167.37	$167.35	$167.40
Purchase #6	$192.56	8.279%	$208.502	$208.50	$208.50	$208.50
Purchase #7	$166.82	9.633%	$182.8898	$182.89	$182.90	$182.90
7 purchase totals =	$957.00		$1,051.8908	$1,051.88	$1,051.85	$1,051.90