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	$213.25	12.799%	$240.5439	$240.54	$240.55	$240.50
Purchase #2	$74.46	5.860%	$78.8234	$78.82	$78.80	$78.80
Purchase #3	$245.41	4.396%	$256.1982	$256.20	$256.20	$256.20
Purchase #4	$139.73	13.752%	$158.9457	$158.95	$158.95	$158.90
Purchase #5	$234.76	13.246%	$265.8563	$265.86	$265.85	$265.90
Purchase #6	$213.46	6.247%	$226.7948	$226.79	$226.80	$226.80
Purchase #7	$105.99	3.190%	$109.3711	$109.37	$109.35	$109.40
7 purchase totals =	$1,227.06		$1,336.5334	$1,336.53	$1,336.50	$1,336.50