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	$68.62	9.866%	$75.39	$75.39	$75.40	$75.40
Purchase #2	$192.57	8.294%	$208.5418	$208.54	$208.55	$208.50
Purchase #3	$105.64	3.642%	$109.4874	$109.49	$109.50	$109.50
Purchase #4	$12.27	12.193%	$13.7661	$13.77	$13.75	$13.80
Purchase #5	$243.38	5.147%	$255.9068	$255.91	$255.90	$255.90
Purchase #6	$179.46	11.652%	$200.3707	$200.37	$200.35	$200.40
Purchase #7	$92.29	6.728%	$98.4993	$98.50	$98.50	$98.50
7 purchase totals =	$894.23		$961.9621	$961.97	$961.95	$962.00