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	$86.56	11.240%	$96.2893	$96.29	$96.30	$96.30
Purchase #2	$23.57	3.405%	$24.3726	$24.37	$24.35	$24.40
Purchase #3	$162.93	7.554%	$175.2377	$175.24	$175.25	$175.20
Purchase #4	$180.81	13.343%	$204.9355	$204.94	$204.95	$204.90
Purchase #5	$69.77	12.198%	$78.2805	$78.28	$78.30	$78.30
Purchase #6	$142.77	5.436%	$150.531	$150.53	$150.55	$150.50
Purchase #7	$196.29	3.860%	$203.8668	$203.87	$203.85	$203.90
7 purchase totals =	$862.70		$933.5134	$933.52	$933.55	$933.50