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	$69.80	9.196%	$76.2188	$76.22	$76.20	$76.20
Purchase #2	$202.55	7.660%	$218.0653	$218.07	$218.05	$218.10
Purchase #3	$37.31	7.399%	$40.0706	$40.07	$40.05	$40.10
Purchase #4	$140.55	7.662%	$151.3189	$151.32	$151.30	$151.30
Purchase #5	$177.90	12.517%	$200.1677	$200.17	$200.15	$200.20
Purchase #6	$32.43	12.570%	$36.5065	$36.51	$36.50	$36.50
Purchase #7	$126.89	3.280%	$131.052	$131.05	$131.05	$131.10
7 purchase totals =	$787.43		$853.3998	$853.41	$853.30	$853.50