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	$205.34	11.214%	$228.3668	$228.37	$228.35	$228.40
Purchase #2	$145.29	13.193%	$164.4581	$164.46	$164.45	$164.50
Purchase #3	$135.27	12.372%	$152.0056	$152.01	$152.00	$152.00
Purchase #4	$228.39	6.306%	$242.7923	$242.79	$242.80	$242.80
Purchase #5	$167.44	10.582%	$185.1585	$185.16	$185.15	$185.20
Purchase #6	$20.31	6.522%	$21.6346	$21.63	$21.65	$21.60
Purchase #7	$144.74	12.220%	$162.4272	$162.43	$162.45	$162.40
7 purchase totals =	$1,046.78		$1,156.8431	$1,156.85	$1,156.85	$1,156.90