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	$196.37	12.351%	$220.6237	$220.62	$220.60	$220.60
Purchase #2	$41.57	13.521%	$47.1907	$47.19	$47.20	$47.20
Purchase #3	$185.88	5.669%	$196.4175	$196.42	$196.40	$196.40
Purchase #4	$242.86	5.368%	$255.8967	$255.90	$255.90	$255.90
Purchase #5	$155.70	8.138%	$168.3709	$168.37	$168.35	$168.40
Purchase #6	$198.55	5.154%	$208.7833	$208.78	$208.80	$208.80
Purchase #7	$123.91	6.449%	$131.901	$131.90	$131.90	$131.90
7 purchase totals =	$1,144.84		$1,229.1838	$1,229.18	$1,229.15	$1,229.20