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	$173.47	13.155%	$196.29	$196.29	$196.30	$196.30
Purchase #2	$9.71	9.671%	$10.6491	$10.65	$10.65	$10.60
Purchase #3	$196.41	11.281%	$218.567	$218.57	$218.55	$218.60
Purchase #4	$242.69	10.113%	$267.2332	$267.23	$267.25	$267.20
Purchase #5	$86.30	13.762%	$98.1766	$98.18	$98.20	$98.20
Purchase #6	$240.59	8.850%	$261.8822	$261.88	$261.90	$261.90
Purchase #7	$138.29	13.105%	$156.4129	$156.41	$156.40	$156.40
7 purchase totals =	$1,087.46		$1,209.2110	$1,209.21	$1,209.25	$1,209.20