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	$167.43	10.807%	$185.5242	$185.52	$185.50	$185.50
Purchase #2	$189.27	3.405%	$195.7146	$195.71	$195.70	$195.70
Purchase #3	$102.26	13.421%	$115.9843	$115.98	$116.00	$116.00
Purchase #4	$103.73	7.526%	$111.5367	$111.54	$111.55	$111.50
Purchase #5	$68.40	3.861%	$71.0409	$71.04	$71.05	$71.00
Purchase #6	$16.88	7.812%	$18.1987	$18.20	$18.20	$18.20
Purchase #7	$94.34	9.348%	$103.1589	$103.16	$103.15	$103.20
7 purchase totals =	$742.31		$801.1583	$801.15	$801.15	$801.10