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	$33.77	12.152%	$37.8737	$37.87	$37.85	$37.90
Purchase #2	$125.33	4.666%	$131.1779	$131.18	$131.20	$131.20
Purchase #3	$162.59	10.149%	$179.0913	$179.09	$179.10	$179.10
Purchase #4	$36.27	11.522%	$40.449	$40.45	$40.45	$40.40
Purchase #5	$192.43	8.593%	$208.9655	$208.97	$208.95	$209.00
Purchase #6	$200.65	8.108%	$216.9187	$216.92	$216.90	$216.90
Purchase #7	$213.98	6.257%	$227.3687	$227.37	$227.35	$227.40
7 purchase totals =	$965.02		$1,041.8448	$1,041.85	$1,041.80	$1,041.90