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	$92.31	12.413%	$103.7684	$103.77	$103.75	$103.80
Purchase #2	$141.65	12.250%	$159.0021	$159.00	$159.00	$159.00
Purchase #3	$38.58	12.767%	$43.5055	$43.51	$43.50	$43.50
Purchase #4	$25.91	11.467%	$28.8811	$28.88	$28.90	$28.90
Purchase #5	$131.78	4.142%	$137.2383	$137.24	$137.25	$137.20
Purchase #6	$200.31	12.253%	$224.854	$224.85	$224.85	$224.90
Purchase #7	$225.27	4.661%	$235.7698	$235.77	$235.75	$235.80
7 purchase totals =	$855.81		$933.0192	$933.02	$933.00	$933.10