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	$101.86	10.835%	$112.8965	$112.90	$112.90	$112.90
Purchase #2	$83.61	8.362%	$90.6015	$90.60	$90.60	$90.60
Purchase #3	$234.53	11.827%	$262.2679	$262.27	$262.25	$262.30
Purchase #4	$59.80	4.238%	$62.3343	$62.33	$62.35	$62.30
Purchase #5	$144.76	7.199%	$155.1813	$155.18	$155.20	$155.20
Purchase #6	$192.37	12.241%	$215.918	$215.92	$215.90	$215.90
Purchase #7	$36.37	4.872%	$38.1419	$38.14	$38.15	$38.10
7 purchase totals =	$853.30		$937.3414	$937.34	$937.35	$937.30