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	$102.43	11.797%	$114.5137	$114.51	$114.50	$114.50
Purchase #2	$9.32	13.445%	$10.5731	$10.57	$10.55	$10.60
Purchase #3	$6.25	4.658%	$6.5411	$6.54	$6.55	$6.50
Purchase #4	$56.56	6.755%	$60.3806	$60.38	$60.40	$60.40
Purchase #5	$87.62	10.569%	$96.8806	$96.88	$96.90	$96.90
Purchase #6	$196.96	9.870%	$216.4	$216.40	$216.40	$216.40
Purchase #7	$90.73	13.360%	$102.8515	$102.85	$102.85	$102.90
7 purchase totals =	$549.87		$608.1406	$608.13	$608.15	$608.20