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	$196.69	13.290%	$222.8301	$222.83	$222.85	$222.80
Purchase #2	$203.52	8.136%	$220.0784	$220.08	$220.10	$220.10
Purchase #3	$29.68	12.314%	$33.3348	$33.33	$33.35	$33.30
Purchase #4	$117.42	11.735%	$131.1992	$131.20	$131.20	$131.20
Purchase #5	$42.54	10.209%	$46.8829	$46.88	$46.90	$46.90
Purchase #6	$35.70	5.116%	$37.5264	$37.53	$37.55	$37.50
Purchase #7	$155.50	10.302%	$171.5196	$171.52	$171.50	$171.50
7 purchase totals =	$781.05		$863.3714	$863.37	$863.45	$863.30