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	$106.98	6.735%	$114.1851	$114.19	$114.20	$114.20
Purchase #2	$175.79	5.420%	$185.3178	$185.32	$185.30	$185.30
Purchase #3	$167.80	7.870%	$181.0059	$181.01	$181.00	$181.00
Purchase #4	$12.58	10.417%	$13.8905	$13.89	$13.90	$13.90
Purchase #5	$105.43	8.702%	$114.6045	$114.60	$114.60	$114.60
Purchase #6	$160.51	12.312%	$180.272	$180.27	$180.25	$180.30
Purchase #7	$131.86	10.292%	$145.431	$145.43	$145.45	$145.40
7 purchase totals =	$860.95		$934.7068	$934.71	$934.70	$934.70