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	$110.37	10.820%	$122.312	$122.31	$122.30	$122.30
Purchase #2	$27.94	12.651%	$31.4747	$31.47	$31.45	$31.50
Purchase #3	$39.32	3.550%	$40.7159	$40.72	$40.70	$40.70
Purchase #4	$228.50	3.118%	$235.6246	$235.62	$235.60	$235.60
Purchase #5	$82.93	8.544%	$90.0155	$90.02	$90.00	$90.00
Purchase #6	$5.35	8.757%	$5.8185	$5.82	$5.80	$5.80
Purchase #7	$107.42	3.376%	$111.0465	$111.05	$111.05	$111.00
7 purchase totals =	$601.83		$637.0077	$637.01	$636.90	$636.90