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	$208.86	10.405%	$230.5919	$230.59	$230.60	$230.60
Purchase #2	$116.85	3.106%	$120.4794	$120.48	$120.50	$120.50
Purchase #3	$50.73	3.524%	$52.5177	$52.52	$52.50	$52.50
Purchase #4	$160.57	3.801%	$166.6733	$166.67	$166.65	$166.70
Purchase #5	$45.26	8.554%	$49.1315	$49.13	$49.15	$49.10
Purchase #6	$245.81	4.365%	$256.5396	$256.54	$256.55	$256.50
Purchase #7	$234.78	6.688%	$250.4821	$250.48	$250.50	$250.50
7 purchase totals =	$1,062.86		$1,126.4155	$1,126.41	$1,126.45	$1,126.40