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	$136.57	11.444%	$152.1991	$152.20	$152.20	$152.20
Purchase #2	$40.36	10.278%	$44.5082	$44.51	$44.50	$44.50
Purchase #3	$172.39	13.698%	$196.004	$196.00	$196.00	$196.00
Purchase #4	$35.90	10.834%	$39.7894	$39.79	$39.80	$39.80
Purchase #5	$72.33	8.217%	$78.2734	$78.27	$78.25	$78.30
Purchase #6	$152.52	13.299%	$172.8036	$172.80	$172.80	$172.80
Purchase #7	$144.86	13.255%	$164.0612	$164.06	$164.05	$164.10
7 purchase totals =	$754.93		$847.6389	$847.63	$847.60	$847.70