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	$241.59	10.867%	$267.8436	$267.84	$267.85	$267.80
Purchase #2	$136.57	5.582%	$144.1933	$144.19	$144.20	$144.20
Purchase #3	$155.32	10.593%	$171.773	$171.77	$171.75	$171.80
Purchase #4	$226.40	10.482%	$250.1312	$250.13	$250.15	$250.10
Purchase #5	$49.96	6.604%	$53.2594	$53.26	$53.25	$53.30
Purchase #6	$127.36	12.186%	$142.8801	$142.88	$142.90	$142.90
Purchase #7	$103.98	9.448%	$113.804	$113.80	$113.80	$113.80
7 purchase totals =	$1,041.18		$1,143.8846	$1,143.87	$1,143.90	$1,143.90