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	$196.27	8.303%	$212.5663	$212.57	$212.55	$212.60
Purchase #2	$90.46	12.625%	$101.8806	$101.88	$101.90	$101.90
Purchase #3	$42.52	8.856%	$46.2856	$46.29	$46.30	$46.30
Purchase #4	$123.66	10.437%	$136.5664	$136.57	$136.55	$136.60
Purchase #5	$177.94	7.826%	$191.8656	$191.87	$191.85	$191.90
Purchase #6	$184.38	13.199%	$208.7163	$208.72	$208.70	$208.70
Purchase #7	$33.67	11.584%	$37.5703	$37.57	$37.55	$37.60
7 purchase totals =	$848.90		$935.4511	$935.47	$935.40	$935.60