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	$118.40	4.208%	$123.3823	$123.38	$123.40	$123.40
Purchase #2	$139.74	3.805%	$145.0571	$145.06	$145.05	$145.10
Purchase #3	$73.79	10.598%	$81.6103	$81.61	$81.60	$81.60
Purchase #4	$162.77	12.760%	$183.5395	$183.54	$183.55	$183.50
Purchase #5	$157.78	9.569%	$172.878	$172.88	$172.90	$172.90
Purchase #6	$152.25	7.798%	$164.1225	$164.12	$164.10	$164.10
Purchase #7	$222.39	9.379%	$243.248	$243.25	$243.25	$243.20
7 purchase totals =	$1,027.12		$1,113.8377	$1,113.84	$1,113.85	$1,113.80