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	$124.86	5.648%	$131.9121	$131.91	$131.90	$131.90
Purchase #2	$217.25	13.275%	$246.0899	$246.09	$246.10	$246.10
Purchase #3	$162.26	7.508%	$174.4425	$174.44	$174.45	$174.40
Purchase #4	$112.65	5.295%	$118.6148	$118.61	$118.60	$118.60
Purchase #5	$103.62	7.868%	$111.7728	$111.77	$111.75	$111.80
Purchase #6	$198.98	5.154%	$209.2354	$209.24	$209.25	$209.20
Purchase #7	$166.61	12.777%	$187.8978	$187.90	$187.90	$187.90
7 purchase totals =	$1,086.23		$1,179.9653	$1,179.96	$1,179.95	$1,179.90