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	$152.48	4.859%	$159.889	$159.89	$159.90	$159.90
Purchase #2	$113.31	5.822%	$119.9069	$119.91	$119.90	$119.90
Purchase #3	$131.46	7.271%	$141.0185	$141.02	$141.00	$141.00
Purchase #4	$220.59	6.741%	$235.46	$235.46	$235.45	$235.50
Purchase #5	$33.32	9.653%	$36.5364	$36.54	$36.55	$36.50
Purchase #6	$110.72	10.129%	$121.9348	$121.93	$121.95	$121.90
Purchase #7	$103.89	6.627%	$110.7748	$110.77	$110.75	$110.80
7 purchase totals =	$865.77		$925.5204	$925.52	$925.50	$925.50