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	$115.92	9.847%	$127.3346	$127.33	$127.35	$127.30
Purchase #2	$222.63	8.490%	$241.5313	$241.53	$241.55	$241.50
Purchase #3	$210.64	7.693%	$226.8445	$226.84	$226.85	$226.80
Purchase #4	$139.56	9.372%	$152.6396	$152.64	$152.65	$152.60
Purchase #5	$221.96	12.117%	$248.8549	$248.85	$248.85	$248.90
Purchase #6	$130.39	9.317%	$142.5384	$142.54	$142.55	$142.50
Purchase #7	$9.48	12.460%	$10.6612	$10.66	$10.65	$10.70
7 purchase totals =	$1,050.58		$1,150.4045	$1,150.39	$1,150.45	$1,150.30