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	$179.79	9.272%	$196.4601	$196.46	$196.45	$196.50
Purchase #2	$216.34	5.306%	$227.819	$227.82	$227.80	$227.80
Purchase #3	$27.50	12.743%	$31.0043	$31.00	$31.00	$31.00
Purchase #4	$141.61	6.171%	$150.3488	$150.35	$150.35	$150.30
Purchase #5	$88.90	5.822%	$94.0758	$94.08	$94.10	$94.10
Purchase #6	$124.39	5.481%	$131.2078	$131.21	$131.20	$131.20
Purchase #7	$177.62	5.771%	$187.8705	$187.87	$187.85	$187.90
7 purchase totals =	$956.15		$1,018.7863	$1,018.79	$1,018.75	$1,018.80