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	$245.32	4.244%	$255.7314	$255.73	$255.75	$255.70
Purchase #2	$27.31	3.667%	$28.3115	$28.31	$28.30	$28.30
Purchase #3	$235.76	8.554%	$255.9269	$255.93	$255.95	$255.90
Purchase #4	$130.91	4.652%	$136.9999	$137.00	$137.00	$137.00
Purchase #5	$43.64	12.309%	$49.0116	$49.01	$49.00	$49.00
Purchase #6	$135.37	3.396%	$139.9672	$139.97	$139.95	$140.00
Purchase #7	$143.25	4.790%	$150.1117	$150.11	$150.10	$150.10
7 purchase totals =	$961.56		$1,016.0602	$1,016.06	$1,016.05	$1,016.00