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	$73.76	13.800%	$83.9389	$83.94	$83.95	$83.90
Purchase #2	$164.85	9.811%	$181.0234	$181.02	$181.00	$181.00
Purchase #3	$154.30	12.140%	$173.032	$173.03	$173.05	$173.00
Purchase #4	$147.52	9.522%	$161.5669	$161.57	$161.55	$161.60
Purchase #5	$180.55	9.826%	$198.2908	$198.29	$198.30	$198.30
Purchase #6	$187.52	6.772%	$200.2189	$200.22	$200.20	$200.20
Purchase #7	$83.70	6.610%	$89.2326	$89.23	$89.25	$89.20
7 purchase totals =	$992.20		$1,087.3035	$1,087.30	$1,087.30	$1,087.20