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	$96.99	10.572%	$107.2438	$107.24	$107.25	$107.20
Purchase #2	$29.71	5.575%	$31.3663	$31.37	$31.35	$31.40
Purchase #3	$229.75	10.225%	$253.2419	$253.24	$253.25	$253.20
Purchase #4	$175.99	11.611%	$196.4242	$196.42	$196.40	$196.40
Purchase #5	$228.38	4.377%	$238.3762	$238.38	$238.40	$238.40
Purchase #6	$129.56	10.299%	$142.9034	$142.90	$142.90	$142.90
Purchase #7	$25.86	9.466%	$28.3079	$28.31	$28.30	$28.30
7 purchase totals =	$916.24		$997.8637	$997.86	$997.85	$997.80