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	$86.51	5.800%	$91.5276	$91.53	$91.55	$91.50
Purchase #2	$166.49	11.448%	$185.5498	$185.55	$185.55	$185.50
Purchase #3	$150.93	11.193%	$167.8236	$167.82	$167.80	$167.80
Purchase #4	$219.30	8.714%	$238.4098	$238.41	$238.40	$238.40
Purchase #5	$176.69	13.706%	$200.9071	$200.91	$200.90	$200.90
Purchase #6	$112.37	6.574%	$119.7572	$119.76	$119.75	$119.80
Purchase #7	$215.40	3.864%	$223.7231	$223.72	$223.70	$223.70
7 purchase totals =	$1,127.69		$1,227.6982	$1,227.70	$1,227.65	$1,227.60