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	$132.45	3.669%	$137.3096	$137.31	$137.30	$137.30
Purchase #2	$195.91	9.211%	$213.9553	$213.96	$213.95	$214.00
Purchase #3	$203.61	9.396%	$222.7412	$222.74	$222.75	$222.70
Purchase #4	$178.30	12.469%	$200.5322	$200.53	$200.55	$200.50
Purchase #5	$106.55	10.428%	$117.661	$117.66	$117.65	$117.70
Purchase #6	$125.54	4.124%	$130.7173	$130.72	$130.70	$130.70
Purchase #7	$72.72	8.383%	$78.8161	$78.82	$78.80	$78.80
7 purchase totals =	$1,015.08		$1,101.7327	$1,101.74	$1,101.70	$1,101.70