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	$175.86	9.193%	$192.0268	$192.03	$192.05	$192.00
Purchase #2	$127.57	7.581%	$137.2411	$137.24	$137.25	$137.20
Purchase #3	$85.91	6.285%	$91.3094	$91.31	$91.30	$91.30
Purchase #4	$156.94	4.850%	$164.5516	$164.55	$164.55	$164.60
Purchase #5	$150.80	7.528%	$162.1522	$162.15	$162.15	$162.20
Purchase #6	$107.69	3.833%	$111.8178	$111.82	$111.80	$111.80
Purchase #7	$66.86	8.865%	$72.7871	$72.79	$72.80	$72.80
7 purchase totals =	$871.63		$931.8860	$931.89	$931.90	$931.90