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	$63.55	4.601%	$66.4739	$66.47	$66.45	$66.50
Purchase #2	$76.50	6.807%	$81.7074	$81.71	$81.70	$81.70
Purchase #3	$160.31	6.690%	$171.0347	$171.03	$171.05	$171.00
Purchase #4	$224.82	11.442%	$250.5439	$250.54	$250.55	$250.50
Purchase #5	$202.31	4.262%	$210.9325	$210.93	$210.95	$210.90
Purchase #6	$184.94	7.761%	$199.2932	$199.29	$199.30	$199.30
Purchase #7	$152.70	6.701%	$162.9324	$162.93	$162.95	$162.90
7 purchase totals =	$1,065.13		$1,142.9180	$1,142.90	$1,142.95	$1,142.80