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	$143.71	10.221%	$158.3986	$158.40	$158.40	$158.40
Purchase #2	$73.91	6.653%	$78.8272	$78.83	$78.85	$78.80
Purchase #3	$246.91	3.381%	$255.258	$255.26	$255.25	$255.30
Purchase #4	$245.50	9.865%	$269.7186	$269.72	$269.70	$269.70
Purchase #5	$158.71	8.578%	$172.3241	$172.32	$172.30	$172.30
Purchase #6	$86.90	8.821%	$94.5654	$94.57	$94.55	$94.60
Purchase #7	$142.82	13.227%	$161.7108	$161.71	$161.70	$161.70
7 purchase totals =	$1,098.46		$1,190.8027	$1,190.81	$1,190.75	$1,190.80