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	$214.71	3.575%	$222.3859	$222.39	$222.40	$222.40
Purchase #2	$158.60	10.172%	$174.7328	$174.73	$174.75	$174.70
Purchase #3	$180.62	6.874%	$193.0358	$193.04	$193.05	$193.00
Purchase #4	$214.69	4.374%	$224.0805	$224.08	$224.10	$224.10
Purchase #5	$31.60	12.336%	$35.4982	$35.50	$35.50	$35.50
Purchase #6	$90.35	7.236%	$96.8877	$96.89	$96.90	$96.90
Purchase #7	$51.32	8.805%	$55.8387	$55.84	$55.85	$55.80
7 purchase totals =	$941.89		$1,002.4596	$1,002.47	$1,002.55	$1,002.40