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	$248.67	5.168%	$261.5213	$261.52	$261.50	$261.50
Purchase #2	$152.71	7.650%	$164.3923	$164.39	$164.40	$164.40
Purchase #3	$246.92	3.108%	$254.5943	$254.59	$254.60	$254.60
Purchase #4	$88.84	8.120%	$96.0538	$96.05	$96.05	$96.10
Purchase #5	$199.25	3.208%	$205.6419	$205.64	$205.65	$205.60
Purchase #6	$78.61	10.486%	$86.853	$86.85	$86.85	$86.90
Purchase #7	$90.72	6.750%	$96.8436	$96.84	$96.85	$96.80
7 purchase totals =	$1,105.72		$1,165.9002	$1,165.88	$1,165.90	$1,165.90