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	$68.85	13.822%	$78.3664	$78.37	$78.35	$78.40
Purchase #2	$178.83	7.673%	$192.5516	$192.55	$192.55	$192.60
Purchase #3	$213.96	4.595%	$223.7915	$223.79	$223.80	$223.80
Purchase #4	$160.32	3.850%	$166.4923	$166.49	$166.50	$166.50
Purchase #5	$156.40	5.153%	$164.4593	$164.46	$164.45	$164.50
Purchase #6	$211.33	8.155%	$228.564	$228.56	$228.55	$228.60
Purchase #7	$59.33	9.695%	$65.082	$65.08	$65.10	$65.10
7 purchase totals =	$1,049.02		$1,119.3071	$1,119.30	$1,119.30	$1,119.50