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	$135.78	8.372%	$147.1475	$147.15	$147.15	$147.10
Purchase #2	$186.45	5.258%	$196.2535	$196.25	$196.25	$196.30
Purchase #3	$227.95	3.662%	$236.2975	$236.30	$236.30	$236.30
Purchase #4	$66.55	13.725%	$75.684	$75.68	$75.70	$75.70
Purchase #5	$155.75	13.335%	$176.5193	$176.52	$176.50	$176.50
Purchase #6	$80.96	10.382%	$89.3653	$89.37	$89.35	$89.40
Purchase #7	$120.88	8.827%	$131.5501	$131.55	$131.55	$131.60
7 purchase totals =	$974.32		$1,052.8172	$1,052.82	$1,052.80	$1,052.90