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	$52.60	13.566%	$59.7357	$59.74	$59.75	$59.70
Purchase #2	$163.67	6.518%	$174.338	$174.34	$174.35	$174.30
Purchase #3	$38.38	13.673%	$43.6277	$43.63	$43.65	$43.60
Purchase #4	$37.88	6.342%	$40.2823	$40.28	$40.30	$40.30
Purchase #5	$155.82	6.198%	$165.4777	$165.48	$165.50	$165.50
Purchase #6	$206.31	5.471%	$217.5972	$217.60	$217.60	$217.60
Purchase #7	$142.25	8.812%	$154.7851	$154.79	$154.80	$154.80
7 purchase totals =	$796.91		$855.8437	$855.86	$855.95	$855.80