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	$89.39	13.663%	$101.6034	$101.60	$101.60	$101.60
Purchase #2	$136.43	3.405%	$141.0754	$141.08	$141.10	$141.10
Purchase #3	$95.79	11.129%	$106.4505	$106.45	$106.45	$106.50
Purchase #4	$109.74	5.327%	$115.5858	$115.59	$115.60	$115.60
Purchase #5	$124.53	12.390%	$139.9593	$139.96	$139.95	$140.00
Purchase #6	$163.83	11.330%	$182.3919	$182.39	$182.40	$182.40
Purchase #7	$237.79	7.567%	$255.7836	$255.78	$255.80	$255.80
7 purchase totals =	$957.50		$1,042.8499	$1,042.85	$1,042.90	$1,043.00