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	$104.43	7.737%	$112.5097	$112.51	$112.50	$112.50
Purchase #2	$99.36	13.693%	$112.9654	$112.97	$112.95	$113.00
Purchase #3	$158.85	10.750%	$175.9264	$175.93	$175.95	$175.90
Purchase #4	$247.98	9.571%	$271.7142	$271.71	$271.70	$271.70
Purchase #5	$180.61	5.659%	$190.8307	$190.83	$190.85	$190.80
Purchase #6	$49.72	12.502%	$55.936	$55.94	$55.95	$55.90
Purchase #7	$174.56	8.431%	$189.2772	$189.28	$189.30	$189.30
7 purchase totals =	$1,015.51		$1,109.1596	$1,109.17	$1,109.20	$1,109.10