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	$123.91	13.376%	$140.4842	$140.48	$140.50	$140.50
Purchase #2	$82.38	7.624%	$88.6607	$88.66	$88.65	$88.70
Purchase #3	$225.76	5.437%	$238.0346	$238.03	$238.05	$238.00
Purchase #4	$170.37	13.199%	$192.8571	$192.86	$192.85	$192.90
Purchase #5	$191.51	4.161%	$199.4787	$199.48	$199.50	$199.50
Purchase #6	$101.59	9.350%	$111.0887	$111.09	$111.10	$111.10
Purchase #7	$69.99	5.346%	$73.7317	$73.73	$73.75	$73.70
7 purchase totals =	$965.51		$1,044.3357	$1,044.33	$1,044.40	$1,044.40