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	$156.58	5.835%	$165.7164	$165.72	$165.70	$165.70
Purchase #2	$226.85	6.264%	$241.0599	$241.06	$241.05	$241.10
Purchase #3	$49.79	9.324%	$54.4324	$54.43	$54.45	$54.40
Purchase #4	$202.48	3.182%	$208.9229	$208.92	$208.90	$208.90
Purchase #5	$57.78	3.651%	$59.8895	$59.89	$59.90	$59.90
Purchase #6	$6.40	8.123%	$6.9199	$6.92	$6.90	$6.90
Purchase #7	$248.79	8.533%	$270.0193	$270.02	$270.00	$270.00
7 purchase totals =	$948.67		$1,006.9603	$1,006.96	$1,006.90	$1,006.90