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	$239.36	13.501%	$271.676	$271.68	$271.70	$271.70
Purchase #2	$212.30	7.527%	$228.2798	$228.28	$228.30	$228.30
Purchase #3	$170.33	12.650%	$191.8767	$191.88	$191.90	$191.90
Purchase #4	$194.31	10.612%	$214.9302	$214.93	$214.95	$214.90
Purchase #5	$185.90	5.695%	$196.487	$196.49	$196.50	$196.50
Purchase #6	$99.36	12.619%	$111.8982	$111.90	$111.90	$111.90
Purchase #7	$182.70	9.780%	$200.5681	$200.57	$200.55	$200.60
7 purchase totals =	$1,284.26		$1,415.7160	$1,415.73	$1,415.80	$1,415.80