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	$40.77	10.493%	$45.048	$45.05	$45.05	$45.00
Purchase #2	$135.55	12.554%	$152.5669	$152.57	$152.55	$152.60
Purchase #3	$116.86	9.451%	$127.9044	$127.90	$127.90	$127.90
Purchase #4	$186.90	12.458%	$210.184	$210.18	$210.20	$210.20
Purchase #5	$249.74	11.573%	$278.6424	$278.64	$278.65	$278.60
Purchase #6	$193.82	11.134%	$215.3999	$215.40	$215.40	$215.40
Purchase #7	$8.94	10.544%	$9.8826	$9.88	$9.90	$9.90
7 purchase totals =	$932.58		$1,039.6282	$1,039.62	$1,039.65	$1,039.60