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	$64.95	11.503%	$72.4212	$72.42	$72.40	$72.40
Purchase #2	$42.69	4.140%	$44.4574	$44.46	$44.45	$44.50
Purchase #3	$57.94	12.389%	$65.1182	$65.12	$65.10	$65.10
Purchase #4	$108.96	9.770%	$119.6054	$119.61	$119.60	$119.60
Purchase #5	$82.73	12.801%	$93.3203	$93.32	$93.30	$93.30
Purchase #6	$113.48	4.143%	$118.1815	$118.18	$118.20	$118.20
Purchase #7	$211.70	11.671%	$236.4075	$236.41	$236.40	$236.40
7 purchase totals =	$682.45		$749.5115	$749.52	$749.45	$749.50