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	$67.90	6.807%	$72.522	$72.52	$72.50	$72.50
Purchase #2	$192.55	6.797%	$205.6376	$205.64	$205.65	$205.60
Purchase #3	$101.55	9.477%	$111.1739	$111.17	$111.15	$111.20
Purchase #4	$106.30	9.321%	$116.2082	$116.21	$116.20	$116.20
Purchase #5	$223.83	8.412%	$242.6586	$242.66	$242.65	$242.70
Purchase #6	$220.88	7.758%	$238.0159	$238.02	$238.00	$238.00
Purchase #7	$244.36	4.768%	$256.0111	$256.01	$256.00	$256.00
7 purchase totals =	$1,157.37		$1,242.2273	$1,242.23	$1,242.15	$1,242.20