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	$217.80	3.716%	$225.8934	$225.89	$225.90	$225.90
Purchase #2	$59.34	13.293%	$67.2281	$67.23	$67.25	$67.20
Purchase #3	$148.88	13.329%	$168.7242	$168.72	$168.70	$168.70
Purchase #4	$96.98	8.792%	$105.5065	$105.51	$105.50	$105.50
Purchase #5	$156.26	11.518%	$174.258	$174.26	$174.25	$174.30
Purchase #6	$220.59	6.110%	$234.068	$234.07	$234.05	$234.10
Purchase #7	$153.90	6.445%	$163.8189	$163.82	$163.80	$163.80
7 purchase totals =	$1,053.75		$1,139.4971	$1,139.50	$1,139.45	$1,139.50