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	$164.61	7.196%	$176.4553	$176.46	$176.45	$176.50
Purchase #2	$239.53	13.386%	$271.5935	$271.59	$271.60	$271.60
Purchase #3	$181.88	4.344%	$189.7809	$189.78	$189.80	$189.80
Purchase #4	$207.82	3.820%	$215.7587	$215.76	$215.75	$215.80
Purchase #5	$184.86	6.447%	$196.7779	$196.78	$196.80	$196.80
Purchase #6	$111.53	12.153%	$125.0842	$125.08	$125.10	$125.10
Purchase #7	$171.96	11.297%	$191.3863	$191.39	$191.40	$191.40
7 purchase totals =	$1,262.19		$1,366.8368	$1,366.84	$1,366.90	$1,367.00