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	$113.70	9.509%	$124.5117	$124.51	$124.50	$124.50
Purchase #2	$191.38	10.161%	$210.8261	$210.83	$210.85	$210.80
Purchase #3	$75.67	8.508%	$82.108	$82.11	$82.10	$82.10
Purchase #4	$180.92	8.410%	$196.1354	$196.14	$196.15	$196.10
Purchase #5	$177.99	5.121%	$187.1049	$187.10	$187.10	$187.10
Purchase #6	$40.59	12.732%	$45.7579	$45.76	$45.75	$45.80
Purchase #7	$216.56	6.387%	$230.3917	$230.39	$230.40	$230.40
7 purchase totals =	$996.81		$1,076.8357	$1,076.84	$1,076.85	$1,076.80