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	$235.82	13.504%	$267.6651	$267.67	$267.65	$267.70
Purchase #2	$86.33	11.535%	$96.2882	$96.29	$96.30	$96.30
Purchase #3	$17.86	3.705%	$18.5217	$18.52	$18.50	$18.50
Purchase #4	$95.83	7.792%	$103.2971	$103.30	$103.30	$103.30
Purchase #5	$209.37	3.663%	$217.0392	$217.04	$217.05	$217.00
Purchase #6	$166.93	7.680%	$179.7502	$179.75	$179.75	$179.80
Purchase #7	$184.43	6.214%	$195.8905	$195.89	$195.90	$195.90
7 purchase totals =	$996.57		$1,078.4520	$1,078.46	$1,078.45	$1,078.50