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	$100.33	7.553%	$107.9079	$107.91	$107.90	$107.90
Purchase #2	$168.50	5.572%	$177.8888	$177.89	$177.90	$177.90
Purchase #3	$69.51	3.278%	$71.7885	$71.79	$71.80	$71.80
Purchase #4	$10.25	9.702%	$11.2445	$11.24	$11.25	$11.20
Purchase #5	$154.27	7.262%	$165.4731	$165.47	$165.45	$165.50
Purchase #6	$62.55	3.650%	$64.8331	$64.83	$64.85	$64.80
Purchase #7	$140.82	12.873%	$158.9478	$158.95	$158.95	$158.90
7 purchase totals =	$706.23		$758.0837	$758.08	$758.10	$758.00