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	$126.65	11.494%	$141.2072	$141.21	$141.20	$141.20
Purchase #2	$117.69	11.771%	$131.5433	$131.54	$131.55	$131.50
Purchase #3	$81.57	10.764%	$90.3502	$90.35	$90.35	$90.40
Purchase #4	$112.55	4.446%	$117.554	$117.55	$117.55	$117.60
Purchase #5	$145.46	12.342%	$163.4127	$163.41	$163.40	$163.40
Purchase #6	$222.81	6.325%	$236.9027	$236.90	$236.90	$236.90
Purchase #7	$150.64	6.800%	$160.8835	$160.88	$160.90	$160.90
7 purchase totals =	$957.37		$1,041.8536	$1,041.84	$1,041.85	$1,041.90