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	$111.51	6.561%	$118.8262	$118.83	$118.85	$118.80
Purchase #2	$246.89	6.846%	$263.7921	$263.79	$263.80	$263.80
Purchase #3	$52.45	6.591%	$55.907	$55.91	$55.90	$55.90
Purchase #4	$125.87	5.574%	$132.886	$132.89	$132.90	$132.90
Purchase #5	$104.73	7.136%	$112.2035	$112.20	$112.20	$112.20
Purchase #6	$234.75	3.265%	$242.4146	$242.41	$242.40	$242.40
Purchase #7	$84.44	7.345%	$90.6421	$90.64	$90.65	$90.60
7 purchase totals =	$960.64		$1,016.6715	$1,016.67	$1,016.70	$1,016.60