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	$185.46	4.345%	$193.5182	$193.52	$193.50	$193.50
Purchase #2	$73.91	8.345%	$80.0778	$80.08	$80.10	$80.10
Purchase #3	$75.86	8.718%	$82.4735	$82.47	$82.45	$82.50
Purchase #4	$93.78	10.524%	$103.6494	$103.65	$103.65	$103.60
Purchase #5	$232.77	12.345%	$261.5055	$261.51	$261.50	$261.50
Purchase #6	$220.38	8.825%	$239.8285	$239.83	$239.85	$239.80
Purchase #7	$49.55	12.231%	$55.6105	$55.61	$55.60	$55.60
7 purchase totals =	$931.71		$1,016.6634	$1,016.67	$1,016.65	$1,016.60