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	$202.84	3.544%	$210.0286	$210.03	$210.05	$210.00
Purchase #2	$163.69	6.490%	$174.3135	$174.31	$174.30	$174.30
Purchase #3	$193.89	12.679%	$218.4733	$218.47	$218.45	$218.50
Purchase #4	$150.54	6.678%	$160.5931	$160.59	$160.60	$160.60
Purchase #5	$79.59	4.138%	$82.8834	$82.88	$82.90	$82.90
Purchase #6	$177.66	7.153%	$190.368	$190.37	$190.35	$190.40
Purchase #7	$40.75	6.337%	$43.3323	$43.33	$43.35	$43.30
7 purchase totals =	$1,008.96		$1,079.9922	$1,079.98	$1,080.00	$1,080.00