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	$137.89	6.287%	$146.5591	$146.56	$146.55	$146.60
Purchase #2	$203.40	12.596%	$229.0203	$229.02	$229.00	$229.00
Purchase #3	$179.36	9.451%	$196.3113	$196.31	$196.30	$196.30
Purchase #4	$97.88	3.664%	$101.4663	$101.47	$101.45	$101.50
Purchase #5	$205.57	9.217%	$224.5174	$224.52	$224.50	$224.50
Purchase #6	$158.91	9.220%	$173.5615	$173.56	$173.55	$173.60
Purchase #7	$54.88	8.640%	$59.6216	$59.62	$59.60	$59.60
7 purchase totals =	$1,037.89		$1,131.0575	$1,131.06	$1,130.95	$1,131.10