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	$136.82	3.220%	$141.2256	$141.23	$141.25	$141.20
Purchase #2	$116.88	13.194%	$132.3011	$132.30	$132.30	$132.30
Purchase #3	$202.84	3.604%	$210.1504	$210.15	$210.15	$210.20
Purchase #4	$210.90	7.491%	$226.6985	$226.70	$226.70	$226.70
Purchase #5	$184.25	6.400%	$196.042	$196.04	$196.05	$196.00
Purchase #6	$82.73	4.511%	$86.462	$86.46	$86.45	$86.50
Purchase #7	$120.47	8.270%	$130.4329	$130.43	$130.45	$130.40
7 purchase totals =	$1,054.89		$1,123.3125	$1,123.31	$1,123.35	$1,123.30