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	$61.48	13.754%	$69.936	$69.94	$69.95	$69.90
Purchase #2	$5.78	5.181%	$6.0795	$6.08	$6.10	$6.10
Purchase #3	$59.81	3.497%	$61.9016	$61.90	$61.90	$61.90
Purchase #4	$236.38	7.605%	$254.3567	$254.36	$254.35	$254.40
Purchase #5	$128.87	12.792%	$145.3551	$145.36	$145.35	$145.40
Purchase #6	$159.84	5.395%	$168.4634	$168.46	$168.45	$168.50
Purchase #7	$109.34	3.794%	$113.4884	$113.49	$113.50	$113.50
7 purchase totals =	$761.50		$819.5807	$819.59	$819.60	$819.70