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	$103.49	7.186%	$110.9268	$110.93	$110.95	$110.90
Purchase #2	$64.54	3.250%	$66.6376	$66.64	$66.65	$66.60
Purchase #3	$54.91	8.677%	$59.6745	$59.67	$59.65	$59.70
Purchase #4	$78.36	8.284%	$84.8513	$84.85	$84.85	$84.90
Purchase #5	$52.42	6.556%	$55.8567	$55.86	$55.85	$55.90
Purchase #6	$197.69	12.235%	$221.8774	$221.88	$221.90	$221.90
Purchase #7	$150.91	9.762%	$165.6418	$165.64	$165.65	$165.60
7 purchase totals =	$702.32		$765.4661	$765.47	$765.50	$765.50