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	$146.91	10.724%	$162.6646	$162.66	$162.65	$162.70
Purchase #2	$72.98	7.174%	$78.2156	$78.22	$78.20	$78.20
Purchase #3	$186.92	11.369%	$208.1709	$208.17	$208.15	$208.20
Purchase #4	$70.62	6.494%	$75.2061	$75.21	$75.20	$75.20
Purchase #5	$241.84	5.588%	$255.354	$255.35	$255.35	$255.40
Purchase #6	$24.64	12.125%	$27.6276	$27.63	$27.65	$27.60
Purchase #7	$182.44	7.747%	$196.5736	$196.57	$196.55	$196.60
7 purchase totals =	$926.35		$1,003.8124	$1,003.81	$1,003.75	$1,003.90