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	$35.76	6.380%	$38.0415	$38.04	$38.05	$38.00
Purchase #2	$199.34	5.700%	$210.7024	$210.70	$210.70	$210.70
Purchase #3	$192.38	9.173%	$210.027	$210.03	$210.05	$210.00
Purchase #4	$134.52	5.767%	$142.2778	$142.28	$142.30	$142.30
Purchase #5	$126.87	4.525%	$132.6109	$132.61	$132.60	$132.60
Purchase #6	$145.56	6.173%	$154.5454	$154.55	$154.55	$154.50
Purchase #7	$152.59	12.591%	$171.8026	$171.80	$171.80	$171.80
7 purchase totals =	$987.02		$1,060.0076	$1,060.01	$1,060.05	$1,059.90