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	$80.59	4.156%	$83.9393	$83.94	$83.95	$83.90
Purchase #2	$168.88	7.387%	$181.3552	$181.36	$181.35	$181.40
Purchase #3	$151.73	9.402%	$165.9957	$166.00	$166.00	$166.00
Purchase #4	$41.65	11.414%	$46.4039	$46.40	$46.40	$46.40
Purchase #5	$111.43	12.634%	$125.5081	$125.51	$125.50	$125.50
Purchase #6	$80.95	3.561%	$83.8326	$83.83	$83.85	$83.80
Purchase #7	$155.38	11.378%	$173.0591	$173.06	$173.05	$173.10
7 purchase totals =	$790.61		$860.0939	$860.10	$860.10	$860.10