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	$233.88	9.823%	$256.854	$256.85	$256.85	$256.90
Purchase #2	$74.74	7.464%	$80.3186	$80.32	$80.30	$80.30
Purchase #3	$223.98	7.704%	$241.2354	$241.24	$241.25	$241.20
Purchase #4	$36.40	7.714%	$39.2079	$39.21	$39.20	$39.20
Purchase #5	$186.60	7.409%	$200.4252	$200.43	$200.45	$200.40
Purchase #6	$67.48	7.566%	$72.5855	$72.59	$72.60	$72.60
Purchase #7	$155.71	11.648%	$173.8471	$173.85	$173.85	$173.80
7 purchase totals =	$978.79		$1,064.4737	$1,064.49	$1,064.50	$1,064.40