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	$40.69	7.149%	$43.5989	$43.60	$43.60	$43.60
Purchase #2	$224.82	7.169%	$240.9373	$240.94	$240.95	$240.90
Purchase #3	$85.42	12.599%	$96.1821	$96.18	$96.20	$96.20
Purchase #4	$105.34	4.428%	$110.0045	$110.00	$110.00	$110.00
Purchase #5	$119.95	9.550%	$131.4052	$131.41	$131.40	$131.40
Purchase #6	$177.71	10.755%	$196.8227	$196.82	$196.80	$196.80
Purchase #7	$178.37	10.379%	$196.883	$196.88	$196.90	$196.90
7 purchase totals =	$932.30		$1,015.8337	$1,015.83	$1,015.85	$1,015.80