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	$142.72	13.721%	$162.3026	$162.30	$162.30	$162.30
Purchase #2	$91.88	8.480%	$99.6714	$99.67	$99.65	$99.70
Purchase #3	$183.73	8.293%	$198.9667	$198.97	$198.95	$199.00
Purchase #4	$88.71	4.124%	$92.3684	$92.37	$92.35	$92.40
Purchase #5	$200.49	5.208%	$210.9315	$210.93	$210.95	$210.90
Purchase #6	$114.90	6.110%	$121.9204	$121.92	$121.90	$121.90
Purchase #7	$167.71	4.372%	$175.0423	$175.04	$175.05	$175.00
7 purchase totals =	$990.14		$1,061.2033	$1,061.20	$1,061.15	$1,061.20