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	$215.40	3.617%	$223.191	$223.19	$223.20	$223.20
Purchase #2	$59.85	9.387%	$65.4681	$65.47	$65.45	$65.50
Purchase #3	$204.43	7.851%	$220.4798	$220.48	$220.50	$220.50
Purchase #4	$93.66	6.565%	$99.8088	$99.81	$99.80	$99.80
Purchase #5	$156.82	9.652%	$171.9563	$171.96	$171.95	$172.00
Purchase #6	$203.92	10.117%	$224.5506	$224.55	$224.55	$224.60
Purchase #7	$154.27	13.388%	$174.9237	$174.92	$174.90	$174.90
7 purchase totals =	$1,088.35		$1,180.3783	$1,180.38	$1,180.35	$1,180.50