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	$113.46	12.346%	$127.4678	$127.47	$127.45	$127.50
Purchase #2	$13.45	4.184%	$14.0127	$14.01	$14.00	$14.00
Purchase #3	$128.56	10.285%	$141.7824	$141.78	$141.80	$141.80
Purchase #4	$166.45	6.140%	$176.67	$176.67	$176.65	$176.70
Purchase #5	$179.72	13.346%	$203.7054	$203.71	$203.70	$203.70
Purchase #6	$187.95	13.665%	$213.6334	$213.63	$213.65	$213.60
Purchase #7	$196.27	11.596%	$219.0295	$219.03	$219.05	$219.00
7 purchase totals =	$985.86		$1,096.3012	$1,096.30	$1,096.30	$1,096.30