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	$206.85	12.527%	$232.7621	$232.76	$232.75	$232.80
Purchase #2	$192.86	8.309%	$208.8847	$208.88	$208.90	$208.90
Purchase #3	$85.26	7.754%	$91.8711	$91.87	$91.85	$91.90
Purchase #4	$79.58	13.246%	$90.1212	$90.12	$90.10	$90.10
Purchase #5	$166.46	12.854%	$187.8568	$187.86	$187.85	$187.90
Purchase #6	$94.35	9.728%	$103.5284	$103.53	$103.55	$103.50
Purchase #7	$191.27	4.724%	$200.3056	$200.31	$200.30	$200.30
7 purchase totals =	$1,016.63		$1,115.3299	$1,115.33	$1,115.30	$1,115.40